.NET Sockets are mostly just TCP/IP Sockets, nothing unusual. .NET also has a set of classes such as TCPClient and TCPListener (for building a server), that contain a Socket, and supply additional functionality - and are easier to use than straight Sockets.

I have started playing with networking, and written a TCP script, which I attached to a GUI script. The GUI script has a Text Box and a Send Button, which sends the contents of the Text box via the WriteSocket() function I wrote. In the GUI script, there is also a function that reads (once a second) the ReadSocket() function for incoming data. If it gets data, it then displays it in a second Text box.

The server part of my test software isn't .NET, I wrote a Python/Twisted-based server. Doesn't do much, basically echoes lines back. But, this is a working example of creating a TCP client in Unity

A list of the C# TCP code I wrote, in a file called 's_TCP.cs', is:

using UnityEngine;
using System.Collections;
using System;
using http://System.IO;
using System.Net.Sockets;

public class s_TCP : MonoBehaviour {
    internal Boolean socketReady = false;

    TcpClient mySocket;
    NetworkStream theStream;
    StreamWriter theWriter;
    StreamReader theReader;
    String Host = "localhost";
    Int32 Port = 5111;

    void Start () {
    }
    void Update () {
    }
// **********************************************
    public void setupSocket() {
        try {
            mySocket = new TcpClient(Host, Port);
            theStream = mySocket.GetStream();
            theWriter = new StreamWriter(theStream);
            theReader = new StreamReader(theStream);
            socketReady = true;
        }
        catch (Exception e) {
            Debug.Log("Socket error: " + e);
        }
    }
    public void writeSocket(string theLine) {
        if (!socketReady)
            return;
        String foo = theLine + "\r\n";
        theWriter.Write(foo);
        theWriter.Flush();
    }
    public String readSocket() {
        if (!socketReady)
            return "";
        if (theStream.DataAvailable)
            return theReader.ReadLine();
        return "";
    }
    public void closeSocket() {
        if (!socketReady)
            return;
        theWriter.Close();
        theReader.Close();
        mySocket.Close();
        socketReady = false;
    }
} // end class s_TCP

Hope that helps.

You can use standard .net sockets to communicate with any other socket-based application. You also have access to most of the .net 2.0 API, and with unity pro, you can write c++ DLLs for your project.

So, there are many ways for your projects to interact with 3rd party applications. You can't use java directly with the Unity engine, although there's nothing stopping you from communicating with Java applications.

One common example of this is Unity clients communicating with Smartfox Server (a socket-based multiuser server application written in Java)

Great. that s what I was expecting :). Any chance to find a code example of .NET socket (I m not yet familiar with the .NET paradigm) working with a unity App, especially a C# example? Technically speaking, How will I contact external socket from a unity app... Don't think I have to do that from a script???

Thanks again for the quick help.