Question

I am making a chat room using simple socket-socket connections.
I have a server and client program. The server runs on port 225, and then when I run the client on port 225 so that they can read/write to the sockets, the client instantly stops with the error message

java.net.SocketException: Connection resetJava Result: 1

Why is it throwing this exception? It connects, the line is printed to console, as shown:

try {
    client = new Socket(serverAdress, portNumber);
    System.out.println("Successful connection to server on port " + portNumber + ".");

So why might it not be able to connect?

This is the exception trace…

java.net.SocketException: Connection reset
at java.net.SocketInputStream.read(SocketInputStream.java:168)
at sun.nio.cs.StreamDecoder.readBytes(StreamDecoder.java:264)
at sun.nio.cs.StreamDecoder.implRead(StreamDecoder.java:306)
at sun.nio.cs.StreamDecoder.read(StreamDecoder.java:158)
at java.io.InputStreamReader.read(InputStreamReader.java:167)
at java.io.BufferedReader.fill(BufferedReader.java:136)
at java.io.BufferedReader.readLine(BufferedReader.java:299)
at java.io.BufferedReader.readLine(BufferedReader.java:362)
at schoolroom10.SchoolRoomClient.SchoolRoomClientWindow.main(SchoolRoomClientWindow.java:85)

This is my Server code…

public class SchoolRoomServer {

    // 'server' will create the server over the local port:
    static ServerSocket serverSocket = null;

    //Socket for listening:
    static Socket clientcommunicate = null;

    //portnum is the number of the local port. Change to required port before running.
    static int portnum = 225;

    public static void main(String[] args) throws IOException{
        try {
            serverSocket = new ServerSocket(portnum);
        clientcommunicate = serverSocket.accept();
            Communicate c = new Communicate(Communicate.server);
            Thread t = new Thread(c);
            t.start();
        } catch (UnknownHostException uhe) {
            System.err.println(uhe);
            System.exit(1);
        } catch (IOException ioe) {
            System.err.println(ioe);
            System.exit(1);
        }


    } 
}

class Communicate implements Runnable {
    public static Socket server;
    Communicate(Socket server) {
        Communicate.server = server;
    }
    public void run() {
        String in = "";
        try {
            //i/o for clients:
            PrintStream output = new PrintStream(server.getOutputStream());
            BufferedReader input = new BufferedReader(new InputStreamReader(server.getInputStream()));
            String message;

            //Message handling:
            while(((message = input.readLine()) != null) && (!in.equals("."))) {
                output.println(message);
            }
        } catch (IOException ioe) {
            System.err.println(ioe);
        }
    }
}

Answer 1

‘Connection reset’ usually means you have written to a connection that has already been closed by the other end. Generally speaking this is an applicaton protocol error. However in some circumstances, e.g. where the peer is a browser, or possibly in your case too, it is just an inevitable consequence of the fact that the peer may choose to go away at any time. In these cases, all you can do is close the socket and forget about the connection.