Android客户端套接字无法连接到服务器

Question

I have a server socket listening in my local computer, and Im trying to connect to this from my android phone. I already tested the server socket with a client on the same computer, and they were able to connect.

However, the client from my android phone isnt able to connect to the socket. My computer's firewall is turned off. Both my computer and the phone are connected to the same wifi network. Can someone please help?

Code for the client socket below:

  public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        Thread fst = new Thread(new startConnection());
        fst.start();
    }

 public class startConnection implements Runnable {
        public void run() {
            try {           
                 final InetAddress hostAddr = InetAddress.getByName("192.168.2.1");//This is the local IP of my computer where the serversocket is listening
                        clientSocket = new Socket();
                        clientSocket.bind(null);
                        clientSocket.connect(new InetSocketAddress(hostAddr, 12555),30000);
               } catch (Exception e) {
                        e.printStackTrace();
               } // end TryCatch block 
         }
}

The error that I keep getting is socket connection timeout.Help?

Thanks a lot!

Answer 1

FOund the issue. I was using this piece of code to get the Local IP of the server:

 try {
    ip = InetAddress.getLocalHost();
 }catch (UnknownHostException e) {
      e.printStackTrace();
 }

This was giving something like 192.168.2.1 for the local IP of the server. I then used this address for connecting the client to the server, and the connection never worked.

I had to instead use a number like 10.0.0.9, which then worked. For getting that correct IP, I had to use this code:

  Enumeration<NetworkInterface> nis = null;
                try {
                    nis = NetworkInterface.getNetworkInterfaces();
                } catch (SocketException e1) {
                    // TODO Auto-generated catch block
                    e1.printStackTrace();
                }
                NetworkInterface ni;
                while (nis.hasMoreElements()) {
                    ni = nis.nextElement();
                    try {
                        if (!ni.isLoopback() && ni.isUp()) {
                            for (InterfaceAddress ia : ni.getInterfaceAddresses()) {
                                //filter for ipv4/ipv6
                                if (ia.getAddress().getAddress().length == 4) {
                                    //4 for ipv4, 16 for ipv6
                                    System.out.println(ia.getAddress());
                                }
                            }
                        }
                    } catch (SocketException e) {
                        // TODO Auto-generated catch block
                        e.printStackTrace();
                    }
                }

THis gives me: /10.0.0.9 /192.168.2.1

The first number is the correct one.

Can someone explain from a networking standpoint, whats the difference in these 2 numbers/the code that gets them and why one works?

Thank you!