Is it possible to create C# client to connect to a specific JVM based server (Netty)?

I am working on a C# client for a server that wraps Netty. It is a TCP/IP server and I have tried using C# class TcpClient, but could not write anything onto the server or receive a printed response.

The Netty socket classes include the following: http://docs.jboss.org/netty/3.2/api/org/jboss/netty/channel/socket/nio/NioClientSocketChannelFactory.html http://docs.jboss.org/netty/3.2/api/org/jboss/netty/bootstrap/ClientBootstrap.html

The message is encoded as a byte[] in Java. Part of class PingSerializer, in the server code, reads as follows:

public byte[] requestToBytes(Ping message) {
  return NorbertExampleProtos.Ping.newBuilder().setTimestamp(message.timestamp).build().toByteArray();
}

public Ping requestFromBytes(byte[] bytes) {
  try {
    return new Ping(NorbertExampleProtos.Ping.newBuilder().mergeFrom(bytes).build().getTimestamp());
  } catch (InvalidProtocolBufferException e) {
    System.out.println("Invalid protocol buffer exception " + e.getMessage());
    throw new IllegalArgumentException(e);
  }
}

I would like to know whether it is possible for a client written in C# to connect to the socket, ping the server and print out the server's response, without modifying the server code or using a cross-language development tool such as Apache Thrift or IKVM to handle the messages. Thanks, I would appreciate any help.

Jon Skeet
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Judging by the code sample you've given, it looks like the data is encoded using Protocol Buffers, Google's serialization format.

Fortunately, there are at least two libraries implementing Protocol Buffers for .NET:

  • protobuf-net: Written for .NET from the ground up, this is a good choice if you don't particularly need the C# code to look like the equivalent Java/C++ code.
  • protobuf-csharp-port: This is a port from the Java client code, with some .NET idioms added - so if you're working with Protocol Buffers on multiple platforms, this may be more appropriate. (Disclaimer: I did most of the coding for this port.)

The good news is that the wire format for the two is the same, because it's the standard Protocol Buffer wire format. So if you decide later on that you've made the wrong choice, you don't need to worry about the data format changing.

In terms of communicating with the server, TcpClient should be absolutely fine. You'll need to find out exactly what the protocol is - for example, whether it's Protocol Buffers over HTTP, or something similar. (If it is over HTTP, WebClient would be a simpler approach.) However, beyond that it's straight TCP/IP: you write the bytes to the server, and it should write a reply. You can use Wireshark to look at the traffic between the client and the server, if you need to trace where problems are occurring.

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