Sockets: Send strings from Java to C#?

Question

Hello I need to send string messages from Java program to C# program in real time. There are many examples in the Internet but I can't find anything good for my purpose that is (probably) Java client (sockets code) and c# server (sockets code). For example I tred this: http://mediakey.dk/~cc/java-and-c-client-server-socket-programming/ but without success. (It seems connection can't be established when using that code). I would be especially grateful if anyone could give me a simple working code for this task. Thank you.

Sergey K · Answer

Thanks for trying to help. I think I've found a good working solution. Using UDP sockets: Java code: public void runJavaSocket() { System.out.println(Java Sockets Program has started.); int i=0; try {DatagramSocket socket = new DatagramSocket(); System.out.println(Sending the udp socket...); // Send the Message HI socket.send(toDatagram(HIInetAddress.getByName(127.0.0.1)3800)); while (true) { System.out.println(Sending hi  + i); Thread.currentThread(); Thread.sleep(1000); socket.send(toDatagram(HI  + String.valueOf(i)InetAddress.getByName(127.0.0.1)3800)); i++; } } catch (Exception e) { e.printStackTrace(); } } public DatagramPacket toDatagram( String s InetAddress destIA int destPort) { // Deprecated in Java 1.1 but it works: byte[] buf = new byte[s.length() + 1]; s.getBytes(0 s.length() buf 0); // The correct Java 1.1 approach but it's // Broken (it truncates the String): // byte[] buf = s.getBytes(); return new DatagramPacket(buf buf.length destIA destPort); } C# code: string returnData; byte[] receiveBytes; //ConsoleKeyInfo cki = new ConsoleKeyInfo(); using (UdpClient udpClient = new UdpClient(new IPEndPoint(IPAddress.Parse(127.0.0.1) 3800))) { IPEndPoint remoteIpEndPoint = new IPEndPoint(IPAddress.Parse(127.0.0.1) 3800); while (true) { receiveBytes = udpClient.Receive(ref remoteIpEndPoint); returnData = Encoding.ASCII.GetString(receiveBytes); Console.WriteLine(returnData); } }

Sam Hobbs · Answer

What about a packet sniffer? Do you have one of those? They are designed for diagnosing things like this. Right? If you see the packets going out then you know it is a problem at the other side. Microsoft offers a free packet sniffer and another good free one is Wireshark (formerly Ethereal).

John Penn · Answer

This could be caused by a firewall on the Java machine. Make sure port 1800 is open and accessible.

Sergey K · Answer

So here's my c# code: ______________________________________________ class Program { private StreamWriter swSender; private StreamReader srReceiver; private TcpClient tcpServer; private Thread thrMessaging; private IPAddress ipAddr; private bool Connected; private string receivedData; static void Main(string[] args) { System.Diagnostics.Process.Start(Path.GetFullPath(RunJar.bat)); Console.WriteLine(C# Sockets Program has started.); try { Program prog = new Program(); prog.InitializeConnection(); } catch (Exception e) { Console.WriteLine(e); } Console.ReadLine(); } private void InitializeConnection() { // Parse the IP address string ipAdress = 127.0.0.1; ipAddr = IPAddress.Parse(ipAdress); // Start a new TCP connections to the chat server tcpServer = new TcpClient(); try { tcpServer.Connect(ipAddr 1800); swSender = new StreamWriter(tcpServer.GetStream()); // Start the thread for receiving messages and further communication thrMessaging = new Thread(new ThreadStart(ReceiveMessages)); thrMessaging.Start(); Connected = true; } catch (Exception e2) { Console.WriteLine(e2.ToString()); } } private void ReceiveMessages() { // Receive the response from the server srReceiver = new StreamReader(tcpServer.GetStream()); while (Connected) { String con = srReceiver.ReadLine(); string StringMessage = HttpUtility.UrlDecode(con System.Text.Encoding.UTF8); processMessage(StringMessage); } } private void processMessage(String p) { // do something with the message Console.WriteLine(p); } private void SendMessage(String p) { if (p != ) { p = HttpUtility.UrlEncode(p System.Text.Encoding.UTF8); swSender.WriteLine(p); swSender.Flush(); } } } ______________________________________________ And here's my Java code: ______________________________________________ public class JavaSocket { public void runJavaSocket() { System.out.println(Java Sockets Program has started.); try { Socket s = new Socket(127.0.0.1 1800); s.connect(new InetSocketAddress(127.0.0.1 1800) 10000); while (!s.isConnected()) { s.connect(new InetSocketAddress(127.0.0.1 1800) 10000); } System.out.println(java Socket Connected.); OutputStream out = s.getOutputStream(); out.write(helloFromjavaCode.getBytes()); out.flush(); out.close(); /* ServerSocket ss = new ServerSocket(1800); Socket s = ss.accept(); System.out.println(Client Accepted); BufferedReader br = new BufferedReader(new InputStreamReader( s.getInputStream())); System.out.println(br.readLine()); PrintWriter wr = new PrintWriter(new OutputStreamWriter( s.getOutputStream()) true); wr.println(Welcome to Socket Programming); */ } catch (Exception e) { System.out.println(e); } try { @SuppressWarnings(unused) int a = System.in.read(); } catch (Exception e) {} } } ________________________________________________ Here's the exception that c# program gives: C# Sockets Program has started. System.Net.Sockets.SocketException (0x80004005): No connection could be made bec ause the target machine actively refused it 127.0.0.1:1800 at System.Net.Sockets.Socket.DoConnect(EndPoint endPointSnapshot SocketAddre ss socketAddress) at System.Net.Sockets.Socket.Connect(EndPoint remoteEP) at System.Net.Sockets.TcpClient.Connect(IPEndPoint remoteEP) at System.Net.Sockets.TcpClient.Connect(IPAddress address Int32 port) at CsSocket.Program.InitializeConnection() in C:\Users\Sergii\documents\visua l studio 2010\Projects\CsSocket\CsSocket\Program.cs:line 66 Here's the exception that Java program gives: java.net.ConnectException: Connection refused: connect What is wrong with my code?

Sam Hobbs · Answer

There are many great articles in this web site and some that will likley help you. Have you looked at the articles listed under Our recommended articles at the right side of this window? Also go to the home page of this web site and look at the networking articles. As John Penn indicates there might be a problem with the way you are using the code you are using; the problem might not be the code. An important thing to do in programs is to catch errors and show an adequate amount of diagnostic information.

John Penn · Answer

Are you getting an error message when the connection fails? If so can you post the exception & stack trace here?