Blog Archives
Remoting (part 2, advanced), WCF
WCF improves code concepts substantially. There are templates like “WCF Service Application” in Visual Studio making programming extremely easy. You get results with a few clicks.
I am concentrating on an independent code solution today. This basically is a similar solution to my remoting example in part 1. You can clearly see the differences rather than starting an entirely new project type.
We need two App.config files.
One on the client side
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.serviceModel>
<client>
<endpoint name="ServerInstance" address="net.tcp://localhost/ServerInstance" binding="netTcpBinding" bindingConfiguration="tcp_Unsecured" contract="Shared.MyInterface"/>
</client>
<bindings>
<netTcpBinding>
<binding name="tcp_Unsecured">
<security mode="None" />
</binding>
</netTcpBinding>
</bindings>
</system.serviceModel>
</configuration>
and one on the server-side.
<?xml version="1.0" encoding="utf-8" ?>
<configuration>
<system.serviceModel>
<services>
<service name="Server.ServerInstance">
<endpoint address="net.tcp://localhost/ServerInstance" binding="netTcpBinding" bindingConfiguration="tcp_Unsecured" contract="Shared.MyInterface" />
</service>
</services>
<bindings>
<netTcpBinding>
<binding name="tcp_Unsecured">
<security mode="None" />
</binding>
</netTcpBinding>
</bindings>
</system.serviceModel>
</configuration>
I guess you have already noticed the Shared.MyInterface. This is the same approach as in the classical Remoting. We share data definitions.
using System;
using System.Collections.Generic;
using System.ServiceModel;
namespace Shared {
[ServiceContract(SessionMode = SessionMode.Allowed)]
public interface MyInterface {
[OperationContract]
List<TradeData> GetTrades();
[OperationContract]
string HelloWorld(string xName);
[OperationContract]
DateTime Ping();
} // interface
} // namespace
The shared area also needs our TradeData class, which is used inside the Interface. Do not forget the Serializable attribute. You do not necessarily get an error message. The program can simply refuse proper execution and only provide mind-boggling error messages.
using System;
namespace Shared {
[Serializable]
public class TradeData {
public DateTime tradeTime;
public string ticker;
public double price;
public int quantity;
public override string ToString() {
return tradeTime.ToString("dd.MMM.yy HH:mm:ss ") + ticker + " " + quantity + " @ " + price + " EUR";
} //
public TradeData(DateTime xTradeTime, string xTicker, double xPrice, int xQuantity) {
tradeTime = xTradeTime;
ticker = xTicker;
price = xPrice;
quantity = xQuantity;
} // constructor
} // class
} // namespace
The class ServerInstance is part of the server-side. It inherits MyInterface and adds the required statements of MyInterface.
using System;
using System.Collections.Generic;
using System.ServiceModel;
using Shared;
namespace Server {
[ServiceBehavior(InstanceContextMode = InstanceContextMode.PerCall)]
internal class ServerInstance : MyInterface {
public List<TradeData> GetTrades() {
DateTime lDummyTime = new DateTime(2014, 02, 12, 16, 30, 10);
TradeData lTrade1 = new TradeData(lDummyTime, "DTE", 11.83, 100);
TradeData lTrade2 = new TradeData(lDummyTime.AddSeconds(2), "DAI", 66.45, 300);
TradeData lTrade3 = new TradeData(lDummyTime.AddSeconds(5), "DBK", 35.91, 100);
return new List<TradeData>() { lTrade1, lTrade2, lTrade3 };
} //
public string HelloWorld(string xName) {
return "Hello " + xName;
} //
public DateTime Ping() {
return DateTime.Now;
} //
} // class
} // namespace
The server side code is relatively short. It is more or less a two liner to instantiate a ServiceHost and open it.
using System;
using System.ServiceModel;
using System.Threading;
namespace Server {
public class Program {
public static void Main(string[] arguments) {
Thread.Sleep(10000); // we let the client wait 10 seconds to simulate a server that is down
using (ServiceHost lServiceHost = new ServiceHost(typeof(ServerInstance))) {
lServiceHost.Open();
Console.WriteLine("Service is available.");
Console.ReadKey();
}
} // main
} // class
} // namespace
And the client side is not much longer. Have a look for yourself. Most of the lines are taking care of printing the data to the console window.
using System;
using System.ServiceModel;
using System.ServiceModel.Channels;
using System.Threading;
using Shared;
namespace Client {
public class Program {
public static void Main(string[] args) {
ChannelFactory<MyInterface> lFactory = new ChannelFactory<MyInterface>("ServerInstance");
MyInterface lShared = null;
while (true) {
try {
lShared = lFactory.CreateChannel();
var o = lShared.GetTrades();
var s = lShared.HelloWorld("Mr. Ohta");
var p = lShared.Ping();
Console.WriteLine("GetTrades():");
foreach (var lTrade in o) Console.WriteLine(lTrade.ToString());
Console.WriteLine();
Console.WriteLine("HelloWorld(): " + s);
Console.WriteLine();
Console.WriteLine("Ping(): " + p);
break;
}
catch (Exception ex) {
Console.WriteLine(ex.Message);
Thread.Sleep(2000);
}
finally {
IChannel lChannel = lShared as IChannel;
if (lChannel.State == CommunicationState.Opened) lChannel.Close();
}
}
Console.ReadKey();
} // main
} // class
} // namespace
After starting the client and server concurrently,
you should get output results like these:
SERVER example output:
Service is available.
CLIENT example output:
Could not connect to net.tcp://localhost/ServerInstance. The connection attempt
lasted for a time span of 00:00:02.0521174. TCP error code 10061: No connection
could be made because the target machine actively refused it 127.0.0.1:808.
Could not connect to net.tcp://localhost/ServerInstance. The connection attempt
lasted for a time span of 00:00:02.0391166. TCP error code 10061: No connection
could be made because the target machine actively refused it 127.0.0.1:808.
GetTrades():
12.Feb.14 16:30:10 DTE 100 @ 11.83 EUR
12.Feb.14 16:30:12 DAI 300 @ 66.45 EUR
12.Feb.14 16:30:15 DBK 100 @ 35.91 EURHelloWorld(): Hello Mr. Ohta
Ping(): 17/02/2014 12:30:59
The error messages on the client side are as expected. They are caused by “Thread.Sleep(10000);” on the server side. I thought it would be interesting to show a server which is not running at the time when starting the client.
Put aside all the complex and confusing examples on the internet. This one here is spot on. It provides a nice and comfortable entry point into WCF. The code does not have to be complex.
I recommend YouTube for further WCF explanations.
Remoting (part 1, basics), old school
Before I come to the new WCF style Remoting, I would like to introduce the good old System.Runtime.Remoting namespace.
Remoting is a convenient way to call methods across the network. You don’t have to write messages to trigger methods on the server, wait for results and then analyse feedback messages on the client side. What could be easier than calling server methods directly?
The downside is the slowness and the missing encryption. Nevertheless, if you don’t have many server requests then Remoting is probably the right solution for you. The ease is hard to beat.
We need a library to share the syntax between the server and client. In practice you would compile the following code into a library and implement it on both sides. Don’t be lazy and only share the source code. This cannot work, because two compilers generate two different system object IDs.
In today’s example we are running the code in one Visual Studio process. We are also using the localhost. This is why we do not need an external library on both sides. We are using the same compiler object ID.
The class MarshalByRefObject enables Remoting access to objects across application domain boundaries. We need to inherit this class.
public abstract class RemotingShared : MarshalByRefObject {
public const string RemotingName = "MyRemotingName";
public const string ServerIpAddress = "127.0.0.1";
public const int Port = 65432;
[Serializable]
public class TradeData {
public DateTime tradeTime;
public string ticker;
public double price;
public int quantity;
public override string ToString() {
return tradeTime.ToString("dd.MMM.yy HH:mm:ss ") + ticker + " " + quantity + " @ " + price + " EUR";
} //
public TradeData(DateTime xTradeTime, string xTicker, double xPrice, int xQuantity) {
tradeTime = xTradeTime;
ticker = xTicker;
price = xPrice;
quantity = xQuantity;
} // constructor
} // class
public abstract List<TradeData> GetTrades();
public abstract string HelloWorld(string xName);
public abstract DateTime Ping();
} // class
The server overrides methods of the abstract class RemotingShared by inheriting it. We do not need to create any instance. This is done in the background by the Remoting process. The option WellKnownObjectMode.Singleton makes sure that only one instance will be created and reused. WellKnownObjectMode.SingleCall would create new instances for each incoming message.
public class RemotingSharedDerived : RemotingShared {
public override List<RemotingShared.TradeData> GetTrades() {
DateTime lDummyTime = new DateTime(2014, 02, 12, 16, 30, 10) ;
RemotingShared.TradeData lTrade1 = new TradeData(lDummyTime, "DTE", 11.83, 100);
RemotingShared.TradeData lTrade2 = new TradeData(lDummyTime.AddSeconds(2), "DAI", 66.45, 300);
RemotingShared.TradeData lTrade3 = new TradeData(lDummyTime.AddSeconds(5), "DBK", 35.91, 100);
return new List<TradeData>() { lTrade1, lTrade2, lTrade3 };
} //
public override string HelloWorld(string xName) {
return "Hello " + xName;
} //
public override DateTime Ping() {
return DateTime.Now;
} //
} // class
public static void StartServer() {
TcpChannel lTcpChannel = new TcpChannel(RemotingShared.Port);
ChannelServices.RegisterChannel(lTcpChannel, true);
Type lRemotingSharedType = typeof(RemotingSharedDerived);
RemotingConfiguration.ApplicationName = RemotingShared.RemotingName + "App";
RemotingConfiguration.RegisterWellKnownServiceType(lRemotingSharedType, RemotingShared.RemotingName, WellKnownObjectMode.Singleton);
} //
Let’s have a look at the client now. As usual I kept the code as short as possible. Personally I do not like example programs that include too much redundant information, they can be quite confusing sometimes.
As we are on the localhost, the server has registered a ‘tcp’ channel already. We check if it exists although we already know it does. But the example program would throw an exception otherwise. Keep it in the code, it does make sense when you are remoting between two different IP addresses.
public static void StartClient() {
string lPath = "tcp://" + RemotingShared.ServerIpAddress + ":" + RemotingShared.Port + "/" + RemotingShared.RemotingName;
TcpChannel lTcpChannel = new TcpChannel();
if (!ChannelServices.RegisteredChannels.Any(lChannel => lChannel.ChannelName == lTcpChannel.ChannelName)) {
ChannelServices.RegisterChannel(lTcpChannel, true);
}
RemotingShared lShared = (RemotingShared)Activator.GetObject(typeof(RemotingShared), lPath);
var o = lShared.GetTrades();
var s = lShared.HelloWorld("Mr. Ohta");
var p = lShared.Ping();
Console.WriteLine("GetTrades():");
foreach (var lTrade in o) Console.WriteLine(lTrade.ToString());
Console.WriteLine();
Console.WriteLine("HelloWorld(): " + s);
Console.WriteLine();
Console.WriteLine("Ping(): " + p);
} //
Let’s run the code now.
public static void Test() {
RemotingServer.StartServer();
RemotingClient.StartClient();
Console.WriteLine("\nPress any key to exit.");
Console.ReadKey();
} //
example output:
GetTrades():
12.Feb.14 16:30:10 DTE 100 @ 11.83 EUR
12.Feb.14 16:30:12 DAI 300 @ 66.45 EUR
12.Feb.14 16:30:15 DBK 100 @ 35.91 EURHelloWorld(): Hello Mr. Ohta
Ping(): 12/02/2014 20:36:55
Press any key to exit.
Protocol Buffers (part 3, advanced), Tcp Networking
Ok guys, hardcore. Unfortunately in a different way than I thought 😉
Once again it took a lot of time to prepare the next source code example. It extends the code of my last post.
I removed the ProtoType class, because inheritance is not a real strength of Protobuf-Net. It is possible, but the ease of code maintenance is a definite argument against it. The complexity increases slowly, we cannot afford code that is difficult to change.
In theory we could write a Serialize() method for each class, the result would be extreme performance. You could use the BitConverter class to convert and then merge values without causing too much overhead. And by using Assembler I guess you could even make it 10 times faster again.
I think that all modern protocols lose a lot of time due to the required reflection, which is mainly the mapping of methods and properties. And unlike Assembler the modern languages do not allow to eg. simply write an integer to a memory address and only read the first byte of it.
You can rotate bits or multiply and divide, what is much less efficient.
In C# you can use the Parallel class to boost your performance. Of course the processing time of each code piece has to be substantial, otherwise it takes longer to create tasks than to solve the problems. In slow networks it might even be worth considering packing data before it is sent.
I replaced the ProtoType class by the Header class, which tells the type of the succeeding data block and also adds a serial identifier. This identifier can be used to receive vital feedbacks. For instance the server tells the client if the data transmission was successful or not. It can also send calculation results or error messages.
The data stream has the following order: header, data, header, data, header, data … except for feedback headers; they do not need data blocks. The enum eType inside the Header class defines all possible data types: ErrorMessage, Feedback, Book or Fable.
As said before I did not use inheritance for the Header class. The code remains legible and there is no spaghetti code to achieve indirect multiple inheritance.
In my last post, the client was sending and the server was receiving data. Now the communication is bidirectional. The client uses two threads, one to send and one to receive. The sending method is still using the BlockingCollection construction and an endless loop on a separate thread.
The server can be connected to several clients simultaneously. To keep it simple I decided sending data without any context switching. This usually blocks threads during the IO operation. I have added tasks inside the event OnMessageBook to give an example on how to avoid this. Nevertheless the send method uses a lock on the client preventing simultaneous write actions on the socket. This is bad practice; you should not apply locks on objects that might be locked in other areas as well. This is out of your scope, you don’t know if the .Net framework or any other code uses a lock on the same object, which could cause undesired behavior. In the below example it would have been better to wrap the client object into another class and apply the lock on that outer shell object. But I guess this is ok in our shorter example. The code was long enough already.
public static void Send(TcpClient xClient, ProtoBufExample.Header xHeader) {
if (xHeader == null) return;
if (xClient == null) return;
lock (xClient) {
NetworkStream lNetworkStream = xClient.GetStream();
....
The above lock problem could be avoided with this:
public class ClientData {
public TcpClient Client { get; private set; }
private DateTime _ConnectedSince;
private string _UserName;
....
public static void Send(ClientData xClient, ProtoBufExample.Header xHeader) {
if (xHeader == null) return;
if (xClient == null) return;
lock (xClient) {
NetworkStream lNetworkStream = xClient.Client.GetStream();
....
And here is the entire source code:
using System;
using System.Collections.Concurrent;
using System.Collections.Generic;
using System.Linq;
using System.Net;
using System.Net.Sockets;
using System.Text;
using System.Threading;
using System.Threading.Tasks;
using ProtoBuf;
namespace DemoApp {
public class ProtoBufExample {
public enum eType : byte { eError = 0, eFeedback, eBook, eFable };
[ProtoContract]
public class Header {
[ProtoMember(1)] public eType objectType;
[ProtoMember(2)] public readonly int serialMessageId;
public object data;
private static int _HeaderSerialId = 0;
public Header(object xData, eType xObjectType, int xSerialMessageId = 0) {
data = xData;
serialMessageId = (xSerialMessageId == 0) ? Interlocked.Increment(ref _HeaderSerialId) : xSerialMessageId;
objectType = xObjectType; // we could use "if typeof(T) ...", but it would be slower, harder to maintain and less legible
} // constructor
// parameterless constructor needed for Protobuf-net
public Header() {
} // constructor
} // class
[ProtoContract]
public class ErrorMessage {
[ProtoMember(1)]
public string Text;
} // class
[ProtoContract]
public class Book {
[ProtoMember(1)] public string author;
[ProtoMember(2, DataFormat = DataFormat.Group)] public List<Fable> stories;
[ProtoMember(3)] public DateTime edition;
[ProtoMember(4)] public int pages;
[ProtoMember(5)] public double price;
[ProtoMember(6)] public bool isEbook;
public override string ToString() {
StringBuilder s = new StringBuilder();
s.Append("by "); s.Append(author);
s.Append(", edition "); s.Append(edition.ToString("dd MMM yyyy"));
s.Append(", pages "); s.Append(pages);
s.Append(", price "); s.Append(price);
s.Append(", isEbook "); s.Append(isEbook);
s.AppendLine();
if (stories != null) foreach (Fable lFable in stories) {
s.Append("title "); s.Append(lFable.title);
s.Append(", rating "); s.Append(lFable.customerRatings.Average()); // Average() is an extension method of "using System.Linq;"
s.AppendLine();
}
return s.ToString();
} //
} // class
[ProtoContract]
public class Fable {
[ProtoMember(1)] public string title;
[ProtoMember(2, DataFormat = DataFormat.Group)]
public double[] customerRatings;
public override string ToString() {
return "title " + title + ", rating " + customerRatings.Average();
} //
} // class
public static Book GetData() {
return new Book {
author = "Aesop",
price = 1.99,
isEbook = false,
edition = new DateTime(1975, 03, 13),
pages = 203,
stories = new List<Fable>(new Fable[] {
new Fable{ title = "The Fox & the Grapes", customerRatings = new double[]{ 0.7, 0.7, 0.8} },
new Fable{ title = "The Goose that Laid the Golden Eggs", customerRatings = new double[]{ 0.6, 0.75, 0.5, 1.0} },
new Fable{ title = "The Cat & the Mice", customerRatings = new double[]{ 0.1, 0.0, 0.3} },
new Fable{ title = "The Mischievous Dog", customerRatings = new double[]{ 0.45, 0.5, 0.4, 0.0, 0.5} }
})
};
} //
} // class
public class PendingFeedbacks {
private readonly ConcurrentDictionary<int, ProtoBufExample.Header> _Messages = new ConcurrentDictionary<int, ProtoBufExample.Header>();
public int Count { get { return _Messages.Count; } }
public void Add(ProtoBufExample.Header xHeader) {
if (xHeader == null) throw new Exception("cannot add a null header");
if (!_Messages.TryAdd(xHeader.serialMessageId, xHeader)) {
throw new Exception("there must be a programming error somewhere");
}
} //
public void Remove(ProtoBufExample.Header xHeader) {
ProtoBufExample.Header lHeader;
if (!_Messages.TryRemove(xHeader.serialMessageId, out lHeader)) {
throw new Exception("there must be a programming error somewhere");
}
switch (xHeader.objectType) {
case ProtoBufExample.eType.eError:
Console.WriteLine("error: " + ((ProtoBufExample.ErrorMessage)xHeader.data).Text);
Console.WriteLine("the message that was sent out was: " + lHeader.objectType + " with serial id " + lHeader.serialMessageId);
Console.WriteLine("please check the log files" + Environment.NewLine);
break;
case ProtoBufExample.eType.eFeedback:
// all ok !
break;
default:
Console.WriteLine("warning: This message type was not expected.");
break;
}
} //
} // class
public static class NetworkTest {
public static void Test() {
NetworkListener lServer = new NetworkListener("127.0.0.1", 65432, "Server");
NetworkClient lClient = new NetworkClient("127.0.0.1", 65432, "Client");
lServer.Connect();
lServer.OnMessageBook += new NetworkListener.dOnMessageBook(OnMessageBook);
lServer.OnMessageFable += new NetworkListener.dOnMessageFable(OnMessageFable);
lClient.Connect();
ProtoBufExample.Header lHeader;
// send a book across the network
ProtoBufExample.Book lBook = ProtoBufExample.GetData();
lHeader = new ProtoBufExample.Header(lBook, ProtoBufExample.eType.eBook);
lClient.Send(lHeader);
System.Threading.Thread.Sleep(1000); // remove this to see the asynchonous processing (the output will look terrible)
// send a fable across the network
lHeader = new ProtoBufExample.Header(lBook.stories[1], ProtoBufExample.eType.eFable);
lClient.Send(lHeader);
System.Threading.Thread.Sleep(1000);
lClient.Disconnect();
lServer.Disconnect();
Console.ReadLine();
}
// demo: synchronous processing
static void OnMessageFable(TcpClient xSender, ProtoBufExample.Header xHeader, ProtoBufExample.Fable xFable) {
Console.WriteLine(Environment.NewLine + "received a fable: ");
Console.WriteLine(xFable.ToString());
// demo: we tell the server that something went wrong
ProtoBufExample.ErrorMessage lErrorMessage = new ProtoBufExample.ErrorMessage() { Text = "The fable was rejected. It is far too short." };
ProtoBufExample.Header lErrorHeader = new ProtoBufExample.Header(lErrorMessage, ProtoBufExample.eType.eError, xHeader.serialMessageId);
NetworkListener.Send(xSender, lErrorHeader);
} //
// demo: asynchronous processing
static void OnMessageBook(TcpClient xSender, ProtoBufExample.Header xHeader, ProtoBufExample.Book xBook) {
Task.Factory.StartNew(() => {
Console.WriteLine(Environment.NewLine + "received a book: ");
Console.WriteLine(xBook.ToString());
// send a feedback without any body to signal all was ok
ProtoBufExample.Header lFeedback = new ProtoBufExample.Header(null, ProtoBufExample.eType.eFeedback, xHeader.serialMessageId);
NetworkListener.Send(xSender, lFeedback);
return;
});
Console.WriteLine("Book event was raised");
} //
} // class
public class NetworkListener {
private bool _ExitLoop = true;
private TcpListener _Listener;
public delegate void dOnMessageBook(TcpClient xSender, ProtoBufExample.Header xHeader, ProtoBufExample.Book xBook);
public event dOnMessageBook OnMessageBook;
public delegate void dOnMessageFable(TcpClient xSender, ProtoBufExample.Header xHeader, ProtoBufExample.Fable xFable);
public event dOnMessageFable OnMessageFable;
private List<TcpClient> _Clients = new List<TcpClient>();
public int Port { get; private set; }
public string IpAddress { get; private set; }
public string ThreadName { get; private set; }
public NetworkListener(string xIpAddress, int xPort, string xThreadName) {
Port = xPort;
IpAddress = xIpAddress;
ThreadName = xThreadName;
} //
public bool Connect() {
if (!_ExitLoop) {
Console.WriteLine("Listener running already");
return false;
}
_ExitLoop = false;
try {
_Listener = new TcpListener(IPAddress.Parse(IpAddress), Port);
_Listener.Start();
Thread lThread = new Thread(new ThreadStart(LoopWaitingForClientsToConnect));
lThread.IsBackground = true;
lThread.Name = ThreadName + "WaitingForClients";
lThread.Start();
return true;
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
return false;
} //
public void Disconnect() {
_ExitLoop = true;
lock (_Clients) {
foreach (TcpClient lClient in _Clients) lClient.Close();
_Clients.Clear();
}
} //
private void LoopWaitingForClientsToConnect() {
try {
while (!_ExitLoop) {
Console.WriteLine("waiting for a client");
TcpClient lClient = _Listener.AcceptTcpClient();
string lClientIpAddress = lClient.Client.LocalEndPoint.ToString();
Console.WriteLine("new client connecting: " + lClientIpAddress);
if (_ExitLoop) break;
lock (_Clients) _Clients.Add(lClient);
Thread lThread = new Thread(new ParameterizedThreadStart(LoopRead));
lThread.IsBackground = true;
lThread.Name = ThreadName + "CommunicatingWithClient";
lThread.Start(lClient);
}
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
finally {
_ExitLoop = true;
if (_Listener != null) _Listener.Stop();
}
} //
private void LoopRead(object xClient) {
TcpClient lClient = xClient as TcpClient;
NetworkStream lNetworkStream = lClient.GetStream();
while (!_ExitLoop) {
try {
ProtoBufExample.Header lHeader = ProtoBuf.Serializer.DeserializeWithLengthPrefix<ProtoBufExample.Header>(lNetworkStream, ProtoBuf.PrefixStyle.Fixed32);
if (lHeader == null) break; // happens during shutdown process
switch (lHeader.objectType) {
case ProtoBufExample.eType.eBook:
ProtoBufExample.Book lBook = ProtoBuf.Serializer.DeserializeWithLengthPrefix<ProtoBufExample.Book>(lNetworkStream, ProtoBuf.PrefixStyle.Fixed32);
if (lBook == null) break;
lHeader.data = lBook; // not necessary, but nicer
dOnMessageBook lEventBook = OnMessageBook;
if (lEventBook == null) continue;
lEventBook(lClient, lHeader, lBook);
break;
case ProtoBufExample.eType.eFable:
ProtoBufExample.Fable lFable = ProtoBuf.Serializer.DeserializeWithLengthPrefix<ProtoBufExample.Fable>(lNetworkStream, ProtoBuf.PrefixStyle.Fixed32);
if (lFable == null) break;
lHeader.data = lFable; // not necessary, but nicer
dOnMessageFable lEventFable = OnMessageFable;
if (lEventFable == null) continue;
lEventFable(lClient, lHeader, lFable);
break;
default:
Console.WriteLine("Mayday, mayday, we are in big trouble.");
break;
}
}
catch (System.IO.IOException) {
if (_ExitLoop) Console.WriteLine("user requested client shutdown");
else Console.WriteLine("disconnected");
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
}
Console.WriteLine("server: listener is shutting down");
} //
public static void Send(TcpClient xClient, ProtoBufExample.Header xHeader) {
if (xHeader == null) return;
if (xClient == null) return;
lock (xClient) {
try {
NetworkStream lNetworkStream = xClient.GetStream();
// send header (most likely a simple feedback)
ProtoBuf.Serializer.SerializeWithLengthPrefix<ProtoBufExample.Header>(lNetworkStream, xHeader, ProtoBuf.PrefixStyle.Fixed32);
// send errors
if (xHeader.objectType != ProtoBufExample.eType.eError) return;
ProtoBuf.Serializer.SerializeWithLengthPrefix<ProtoBufExample.ErrorMessage>(lNetworkStream, (ProtoBufExample.ErrorMessage)xHeader.data, ProtoBuf.PrefixStyle.Fixed32);
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
}
} //
} // class
public class NetworkClient {
public int Port { get; private set; }
public string IpAddress { get; private set; }
public string ThreadName { get; private set; }
private NetworkStream _NetworkStream = null;
private TcpClient _Client = null;
private bool _ExitLoop = true;
private BlockingCollection<ProtoBufExample.Header> _Queue = new BlockingCollection<ProtoBufExample.Header>();
private readonly PendingFeedbacks _PendingFeedbacks = new PendingFeedbacks();
public NetworkClient(string xIpAddress, int xPort, string xThreadName) {
Port = xPort;
IpAddress = xIpAddress;
ThreadName = xThreadName;
} //
public void Connect() {
if (!_ExitLoop) return; // running already
_ExitLoop = false;
_Client = new TcpClient();
_Client.Connect(IpAddress, Port);
_NetworkStream = _Client.GetStream();
Thread lLoopWrite = new Thread(new ThreadStart(LoopWrite));
lLoopWrite.IsBackground = true;
lLoopWrite.Name = ThreadName + "Write";
lLoopWrite.Start();
Thread lLoopRead = new Thread(new ThreadStart(LoopRead));
lLoopRead.IsBackground = true;
lLoopRead.Name = ThreadName + "Read";
lLoopRead.Start();
} //
public void Disconnect() {
_ExitLoop = true;
_Queue.Add(null);
if (_Client != null) _Client.Close();
//if (_NetworkStream != null) _NetworkStream.Close();
} //
public void Send(ProtoBufExample.Header xHeader) {
if (xHeader == null) return;
_PendingFeedbacks.Add(xHeader);
_Queue.Add(xHeader);
} //
private void LoopWrite() {
while (!_ExitLoop) {
try {
ProtoBufExample.Header lHeader = _Queue.Take();
if (lHeader == null) break;
// send header
ProtoBuf.Serializer.SerializeWithLengthPrefix<ProtoBufExample.Header>(_NetworkStream, lHeader, ProtoBuf.PrefixStyle.Fixed32);
// send data
switch (lHeader.objectType) {
case ProtoBufExample.eType.eBook:
ProtoBuf.Serializer.SerializeWithLengthPrefix<ProtoBufExample.Book>(_NetworkStream, (ProtoBufExample.Book)lHeader.data, ProtoBuf.PrefixStyle.Fixed32);
break;
case ProtoBufExample.eType.eFable:
ProtoBuf.Serializer.SerializeWithLengthPrefix<ProtoBufExample.Fable>(_NetworkStream, (ProtoBufExample.Fable)lHeader.data, ProtoBuf.PrefixStyle.Fixed32);
break;
default:
break;
}
}
catch (System.IO.IOException) {
if (_ExitLoop) Console.WriteLine("user requested client shutdown.");
else Console.WriteLine("disconnected");
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
}
_ExitLoop = true;
Console.WriteLine("client: writer is shutting down");
} //
private void LoopRead() {
while (!_ExitLoop) {
try {
ProtoBufExample.Header lHeader = ProtoBuf.Serializer.DeserializeWithLengthPrefix<ProtoBufExample.Header>(_NetworkStream, ProtoBuf.PrefixStyle.Fixed32);
if (lHeader == null) break;
if (lHeader.objectType == ProtoBufExample.eType.eError) {
ProtoBufExample.ErrorMessage lErrorMessage = ProtoBuf.Serializer.DeserializeWithLengthPrefix<ProtoBufExample.ErrorMessage>(_NetworkStream, ProtoBuf.PrefixStyle.Fixed32);
lHeader.data = lErrorMessage;
}
_PendingFeedbacks.Remove(lHeader);
}
catch (System.IO.IOException) {
if (_ExitLoop) Console.WriteLine("user requested client shutdown");
else Console.WriteLine("disconnected");
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
}
Console.WriteLine("client: reader is shutting down");
} //
} // class
} // namespace
example output:
waiting for a client
new client connecting: 127.0.0.1:65432
waiting for a client
Book event was raisedreceived a book:
by Aesop, edition 13 Mar 1975, pages 203, price 1.99, isEbook False
title The Fox & the Grapes, rating 0.733333333333333
title The Goose that Laid the Golden Eggs, rating 0.7125
title The Cat & the Mice, rating 0.133333333333333
title The Mischievous Dog, rating 0.37received a fable:
title The Goose that Laid the Golden Eggs, rating 0.7125
error: The fable was rejected. It is far too short.
the message that was sent out was: eFable with serial id 2
please check the log filesclient: writer is shutting down
server: listener is shutting down
user requested client shutdown
client: reader is shutting down
Protocol Buffers (part 2, advanced), Tcp Networking
There has been no post yesterday. As usual I am preparing the source code for you during my spare time. This is not easy in my current environment. I will have to slow down the post frequency as the source codes are getting longer and more complex.
So, what is on the agenda now? Today we are going to send serialized binary data across the network. I am using the localhost to have a running example. Simply amend the local IP-addresses “127.0.0.1” to whatever suits you.
I wrote a small class (“ProtoType”) to identify objects quickly during the serialization and deserialization process. It is abstract and forms our base class. The class “Book” and “Fable” are nearly unchanged from the previous posts. I just added an override “ToString” in “Fable” to have a nicer output. Both classes must inherit from our abstract base class called “ProtoType”, which avoids implementing an interface and impacting the code legibility more than needed.
public class ProtoBufExample {
public enum eType { Unknown = 0, eBook = 1, eFable };
public abstract class ProtoType {
public readonly eType objectId;
public readonly byte[] objectIdAsBytes;
public ProtoType() {
Type t = this.GetType();
if (t == typeof(ProtoBufExample.Book)) objectId = eType.eBook; // to identify the object before deserialization
else if (t == typeof(ProtoBufExample.Fable)) objectId = eType.eFable; // to identify the object before deserialization
else throw new Exception("object type unknown");
objectIdAsBytes = BitConverter.GetBytes((Int16)objectId);
} // constructor
} // class
[ProtoContract]
public class Book : ProtoType {
[ProtoMember(1)]
public string author;
[ProtoMember(2)]
public List<Fable> stories;
[ProtoMember(3)]
public DateTime edition;
[ProtoMember(4)]
public int pages;
[ProtoMember(5)]
public double price;
[ProtoMember(6)]
public bool isEbook;
public override string ToString() {
StringBuilder s = new StringBuilder();
s.Append("by "); s.Append(author);
s.Append(", edition "); s.Append(edition.ToString("dd MMM yyyy"));
s.Append(", pages "); s.Append(pages);
s.Append(", price "); s.Append(price);
s.Append(", isEbook "); s.Append(isEbook);
s.AppendLine();
if (stories != null) foreach (Fable lFable in stories) {
s.Append("title "); s.Append(lFable.title);
s.Append(", rating "); s.Append(lFable.customerRatings.Average()); // Average() is an extension method of "using System.Linq;"
s.AppendLine();
}
return s.ToString();
} //
} // class
[ProtoContract]
public class Fable : ProtoType {
[ProtoMember(1)]
public string title;
[ProtoMember(2)]
public double[] customerRatings;
public override string ToString() {
return "title " + title + ", rating " + customerRatings.Average();
} //
} // class
public static Book GetData() {
return new Book {
author = "Aesop",
price = 1.99,
isEbook = false,
edition = new DateTime(1975, 03, 13),
pages = 203,
stories = new List<Fable>(new Fable[] {
new Fable{ title = "The Fox & the Grapes", customerRatings = new double[]{ 0.7, 0.7, 0.8} },
new Fable{ title = "The Goose that Laid the Golden Eggs", customerRatings = new double[]{ 0.6, 0.75, 0.5, 1.0} },
new Fable{ title = "The Cat & the Mice", customerRatings = new double[]{ 0.1, 0.0, 0.3} },
new Fable{ title = "The Mischievous Dog", customerRatings = new double[]{ 0.45, 0.5, 0.4, 0.0, 0.5} }
})
};
} //
} // class
The server-side always needs to be started before the client. Otherwise the client would not receive an immediate response from the server. We set up a listener on localhost port 65432 (arbitrary choice) and wait for a client connection. I chose the TCP protocol. It is easy to use and very reliable. We do not need to care about transmission problems. The downside is slowness. I will cover that one in comming posts.
The deserializer on the server-side cannot be run right away. We need to determine the object type first. And here we make use of our “ProtoType” class. The first two bytes of the transmission tell us the type. This is quite important for the speed of the deserialization. You see that the ProtoBuf.Serializer.DeserializeWithLengthPrefix method is generic. The type casting is minimized that way.
public class NetworkListener {
private bool _ExitLoop = true;
private TcpListener _Listener;
public delegate void dOnMessage(object xSender, ProtoBufExample.Book xBook);
public event dOnMessage OnMessage;
private NetworkStream _NetworkStream = null;
public int Port { get; private set; }
public string IpAddress { get; private set; }
public string ThreadName { get; private set; }
public NetworkListener(string xIpAddress, int xPort, string xThreadName) {
Port = xPort;
IpAddress = xIpAddress;
ThreadName = xThreadName;
} //
public bool Connect() {
if (!_ExitLoop) {
Console.WriteLine("Listener running already");
return false;
}
_ExitLoop = false;
try {
_Listener = new TcpListener(IPAddress.Parse(IpAddress), Port);
_Listener.Start();
Thread lThread = new Thread(new ThreadStart(Loop));
lThread.IsBackground = true;
lThread.Name = ThreadName;
lThread.Start();
return true;
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
return false;
} //
public void Disconnect() {
_ExitLoop = true;
_NetworkStream.WriteTimeout = 5; // immediate timeout
} //
private void Loop() {
try {
while (!_ExitLoop) {
Console.WriteLine("Waiting for a client");
using (TcpClient lClient = _Listener.AcceptTcpClient()) {
string lClientIpAddress = lClient.Client.LocalEndPoint.ToString();
Console.WriteLine("New client connecting: " + lClientIpAddress);
using (_NetworkStream = lClient.GetStream()) {
while (!_ExitLoop) {
try {
byte[] lHeader = new byte[2]; // to indentify the object
if (_NetworkStream.Read(lHeader, 0, 2) != 2) break;
int lObjectType = BitConverter.ToInt16(lHeader, 0);
ProtoBufExample.eType lType = (ProtoBufExample.eType)lObjectType;
switch (lType) {
case ProtoBufExample.eType.Unknown:
break;
case ProtoBufExample.eType.eBook:
ProtoBufExample.Book lBook = ProtoBuf.Serializer.DeserializeWithLengthPrefix<ProtoBufExample.Book>(_NetworkStream, ProtoBuf.PrefixStyle.Fixed32);
Console.WriteLine(Environment.NewLine + "received a book: ");
Console.WriteLine(lBook.ToString());
// raise an event
dOnMessage lEvent = OnMessage;
if (lEvent == null) continue;
lEvent(lClient, lBook);
break;
case ProtoBufExample.eType.eFable:
ProtoBufExample.Fable lFable = ProtoBuf.Serializer.DeserializeWithLengthPrefix<ProtoBufExample.Fable>(_NetworkStream, ProtoBuf.PrefixStyle.Fixed32);
Console.WriteLine(Environment.NewLine + "received a fable: ");
Console.WriteLine(lFable.ToString());
break;
default:
Console.WriteLine("Mayday, mayday, we are in big trouble.");
break;
}
}
catch (System.IO.IOException) {
if (_ExitLoop) Console.WriteLine("user requested TcpClient shutdown");
else Console.WriteLine("disconnected");
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
}
Console.WriteLine(Environment.NewLine + "server/listener: shutting down");
}
}
}
}
catch (Exception ex) {
Console.WriteLine(ex.Message);
}
finally {
_ExitLoop = true;
if (_Listener != null) _Listener.Stop();
}
} //
} // class
The client side is straight forward. There is not much processing besides choosing the correct generic type for the serialization process. I used a BlockingCollection to make the context switching easier to read. It is not the fastest solution, but it definitely makes passing objects into a thread loop easy. I am personally no fan of the concurrent collections. They are not as predictable as any custom solution. _Queue.Take(); blocks and waits for data to arrive. It is thread-safe and does not require any object locking.
public class NetworkClient {
public int Port { get; private set; }
public string IpAddress { get; private set; }
public string ThreadName { get; private set; }
private NetworkStream _NetworkStream = null;
private bool _ExitLoop = true;
private BlockingCollection<ProtoBufExample.ProtoType> _Queue = new BlockingCollection<ProtoBufExample.ProtoType>();
public NetworkClient(string xIpAddress, int xPort, string xThreadName) {
Port = xPort;
IpAddress = xIpAddress;
ThreadName = xThreadName;
} //
public void Connect() {
if (!_ExitLoop) return; // running already
_ExitLoop = false;
Thread lThread = new Thread(new ThreadStart(Loop));
lThread.IsBackground = true;
lThread.Name = ThreadName;
lThread.Start();
} //
public void Disconnect() {
_ExitLoop = true;
_Queue.Add(null);
if (_NetworkStream != null) _NetworkStream.ReadTimeout = 100;
} //
public void Send(ProtoBufExample.ProtoType xObject) {
if (xObject == null) return;
_Queue.Add(xObject);
} //
private void Loop() {
try {
using (TcpClient lClient = new TcpClient()) {
lClient.Connect(IpAddress, Port);
using (_NetworkStream = lClient.GetStream()) {
while (!_ExitLoop) {
try {
ProtoBufExample.ProtoType lObject = _Queue.Take();
if (lObject == null) break;
switch (lObject.objectId) {
case ProtoBufExample.eType.eBook:
_NetworkStream.Write(lObject.objectIdAsBytes, 0, 2);
ProtoBuf.Serializer.SerializeWithLengthPrefix<ProtoBufExample.Book>(_NetworkStream, (ProtoBufExample.Book)lObject, ProtoBuf.PrefixStyle.Fixed32);
break;
case ProtoBufExample.eType.eFable:
_NetworkStream.Write(lObject.objectIdAsBytes, 0, 2);
ProtoBuf.Serializer.SerializeWithLengthPrefix<ProtoBufExample.Fable>(_NetworkStream, (ProtoBufExample.Fable)lObject, ProtoBuf.PrefixStyle.Fixed32);
break;
default:
break;
}
}
catch (System.IO.IOException) {
if (_ExitLoop) Console.WriteLine("user requested TcpClient shutdown.");
else Console.WriteLine("disconnected");
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
}
_ExitLoop = true;
Console.WriteLine(Environment.NewLine + "client: shutting down");
}
}
}
catch (Exception ex) { Console.WriteLine(ex.Message); }
} //
} // class
The main program is pretty neat. We get the “Book” data and send it across the localhost. Then we take a single story of the same book and send it again to see if the program deals with the different types properly. Et voilà , it does.
The framing of the serialized data is very important. If you do not frame it, then you cannot determine the type. There are weird examples on the internet. My quick google research showed that people generally do not implement that centerpiece, leaving beginners in the middle of nowhere.
public static class NetworkTest {
public static void Test() {
NetworkListener lServer = new NetworkListener("127.0.0.1", 65432, "Server");
NetworkClient lClient = new NetworkClient("127.0.0.1", 65432, "Client");
lServer.Connect();
lServer.OnMessage += new NetworkListener.dOnMessage(OnBook);
lClient.Connect();
// send a book across the network
ProtoBufExample.Book lBook = ProtoBufExample.GetData();
lClient.Send(lBook);
// send a fable across the network
lClient.Send(lBook.stories[1]);
System.Threading.Thread.Sleep(1000);
lClient.Disconnect();
lServer.Disconnect();
Console.ReadLine();
}
static void OnBook(object xSender, ProtoBufExample.Book xBook) {
Console.WriteLine("Book event was raised");
} //
} //
example output:
Waiting for a client
New client connecting: 127.0.0.1:65432received a book:
by Aesop, edition 13 Mar 1975, pages 203, price 1.99, isEbook False
title The Fox & the Grapes, rating 0.733333333333333
title The Goose that Laid the Golden Eggs, rating 0.7125
title The Cat & the Mice, rating 0.133333333333333
title The Mischievous Dog, rating 0.37Book event was raised
received a fable:
title The Goose that Laid the Golden Eggs, rating 0.7125client: shutting down
server/listener: shutting down
There is one tiny issue with the OnBook event. We receive data on a thread and block the thread as long as it takes to process the event. To avoid thread bottlenecks you should think about forwarding “Book” events to tasks and let them deal with whatever needs to be done asynchronously. I posted about tasks eg. here. ThreadPools and the Parallel class might also be interesting posts in this context.
Protocol Buffers (part 1, basics), follow-up to JSON & XML
I quickly introduced Protocol Buffers in my last post. It is an amazing tool that every programmer should know. The .Net version protobuf-net can be downloaded from here.
On its homepage Protocol Buffers is described with the following words:
Protocol buffers is the name of the binary serialization format used by Google for much of their data communications. It is designed to be:
small in size – efficient data storage (far smaller than xml)
cheap to process – both at the client and server
platform independent – portable between different programming architectures
extensible – to add new data to old messages
This is succinct. Protobuf-net also supports the WCF.
Add the protobuf-net.dll, which is located in the net30 installation directory, to your solution references.
We need some data structure to start with.
public class Book {
public string author;
public List<Fable> stories;
public DateTime edition;
public int pages;
public double price;
public bool isEbook;
} // class
public class Fable {
public string title;
public double[] customerRatings;
} // class
Protocol Buffers uses attributes to identify types to serialize. The ProtoMember attribute needs a positive integer. This can be painful, because you have to avoid overlapping when using inheritance. But integers have a distinct advantage as well. They are much faster than strings. As you are already aware, Protocol Buffers is about speed.
[ProtoContract]
public class Book {
[ProtoMember(1)]
public string author;
[ProtoMember(2)]
public List stories;
[ProtoMember(3)]
public DateTime edition;
[ProtoMember(4)]
public int pages;
[ProtoMember(5)]
public double price;
[ProtoMember(6)]
public bool isEbook;
public override string ToString() {
StringBuilder s = new StringBuilder();
s.Append("by "); s.Append(author);
s.Append(", edition "); s.Append(edition.ToString("dd MMM yyyy"));
s.Append(", pages "); s.Append(pages);
s.Append(", price "); s.Append(price);
s.Append(", isEbook "); s.Append(isEbook);
s.AppendLine();
if (stories != null) foreach (Fable lFable in stories) {
s.Append("title "); s.Append(lFable.title);
s.Append(", rating "); s.Append(lFable.customerRatings.Average());
s.AppendLine();
}
return s.ToString();
} //
} // class
[ProtoContract]
public class Fable {
[ProtoMember(1)]
public string title;
[ProtoMember(2)]
public double[] customerRatings;
} // class
public static Book GetData() {
return new Book {
author = "Aesop",
price = 1.99,
isEbook = false,
edition = new DateTime(1975, 03, 13),
pages = 203,
stories = new List<Fable>(new Fable[] {
new Fable{ title = "The Fox & the Grapes", customerRatings = new double[]{ 0.7, 0.7, 0.8} },
new Fable{ title = "The Goose that Laid the Golden Eggs", customerRatings = new double[]{ 0.6, 0.75, 0.5, 1.0} },
new Fable{ title = "The Cat & the Mice", customerRatings = new double[]{ 0.1, 0.0, 0.3} },
new Fable{ title = "The Mischievous Dog", customerRatings = new double[]{ 0.45, 0.5, 0.4, 0.0, 0.5} }
})
};
} //
Let’s serialize the data now.
public static void SerializeData() {
MemoryStream lStream = new MemoryStream();
BinaryWriter lWriter = new BinaryWriter(lStream); // no "using", because it would close the MemoryStream automatically
Book lBook = GetData();
ProtoBuf.Serializer.Serialize<Book>(lStream, lBook);
lWriter.Flush();
lStream.Position = 0;
using (BinaryReader lReader = new BinaryReader(lStream)) {
for (long i = 0, n = lStream.Length; i < n; i++) {
byte b = lReader.ReadByte();
Console.Write(string.Format("{0:X2} ", b));
if ((i+1) % 20 == 0) Console.WriteLine();
}
Console.WriteLine();
Console.WriteLine();
Console.WriteLine("number of bytes: " + lStream.Length);
}
Console.ReadLine();
} //
example output:
0A 05 41 65 73 6F 70 12 31 0A 14 54 68 65 20 46 6F 78 20 26
20 74 68 65 20 47 72 61 70 65 73 11 66 66 66 66 66 66 E6 3F
11 66 66 66 66 66 66 E6 3F 11 9A 99 99 99 99 99 E9 3F 12 49
0A 23 54 68 65 20 47 6F 6F 73 65 20 74 68 61 74 20 4C 61 69
64 20 74 68 65 20 47 6F 6C 64 65 6E 20 45 67 67 73 11 33 33
33 33 33 33 E3 3F 11 00 00 00 00 00 00 E8 3F 11 00 00 00 00
00 00 E0 3F 11 00 00 00 00 00 00 F0 3F 12 2F 0A 12 54 68 65
20 43 61 74 20 26 20 74 68 65 20 4D 69 63 65 11 9A 99 99 99
99 99 B9 3F 11 00 00 00 00 00 00 00 00 11 33 33 33 33 33 33
D3 3F 12 42 0A 13 54 68 65 20 4D 69 73 63 68 69 65 76 6F 75
73 20 44 6F 67 11 CD CC CC CC CC CC DC 3F 11 00 00 00 00 00
00 E0 3F 11 9A 99 99 99 99 99 D9 3F 11 00 00 00 00 00 00 00
00 11 00 00 00 00 00 00 E0 3F 1A 03 08 D2 1D 20 CB 01 29 D7
A3 70 3D 0A D7 FF 3Fnumber of bytes: 267
And back again: deserialize data.
public static void ToAndFro() {
using (MemoryStream lStream = new MemoryStream()) {
BinaryWriter lWriter = new BinaryWriter(lStream);
Book lBook = GetData();
ProtoBuf.Serializer.Serialize<Book>(lStream, lBook);
lWriter.Flush();
lStream.Position = 0;
Book lCopy = ProtoBuf.Serializer.Deserialize<Book>(lStream);
Console.WriteLine(lCopy.ToString());
}
Console.ReadLine();
} //
example output:
by Aesop, edition 13 Mar 1975, pages 203, price 1.99, isEbook False
title The Fox & the Grapes, rating 0.733333333333333
title The Goose that Laid the Golden Eggs, rating 0.7125
title The Cat & the Mice, rating 0.133333333333333
title The Mischievous Dog, rating 0.37
C# Hardcore Programming 