Java TCP Connection Socket not writing to output stream

Question

I am writing a server for a game which I am coding in java. The output stream won't actually send the information back to the client for some reason. I have tried everything, however closing the socket ends up in the program erroring because of the socket closing before it has written to the output stream. I am unable to figure out why.

EDIT: I have put a lot of the code in this gist. Also, for clarification, the response wasn't sending at all, even if I didn't close the socket. The client was simply waiting for an answer, and not receiving one.

Here is my code.

public class ServerThread extends Thread {

private Socket clientSocket;
private List<Player> players;
public Player player = null;

public ServerThread (Socket clientSocket, List<Player> players)
{
    this.clientSocket = clientSocket;
    this.players = players;
}

public void run()
{
    try {
        BufferedReader br = new BufferedReader(new InputStreamReader(clientSocket.getInputStream()));
        DataOutputStream os = new DataOutputStream(clientSocket.getOutputStream());

        String req = br.readLine();
        br.close();
        String response = buildResponse(req);

        os.writeBytes(response);
        os.flush();
        System.out.println("Sending [ " + response + " ] to " + clientSocket.getInetAddress().getHostAddress());

        player = addPlayerFromRequest(req);
    } catch (IOException ex) {
        Logger.getLogger(ServerThread.class.getName()).log(Level.SEVERE, null, ex);
    } 

    try {
        clientSocket.close();
    } catch (IOException ex) {
        Logger.getLogger(ServerThread.class.getName()).log(Level.SEVERE, null, ex);
    }
}

public String buildResponse(String req)
{
    List<Player> plays;
    plays = players;

    String name = req.split(",")[0];

    String response = "";

    if (plays.size() <= 1) {
        return response;
    }

    for (int i = 0; i < plays.size(); i++) {
        Player p = plays.get(i);
        if (!p.name.equals(name)) {
            response += p.name + "," + p.x + "," + p.y + "," + p.z + "," + p.rx + "," + p.rx + "," + p.rz + ";";
        }
    }
    return response;
}

public Player addPlayerFromRequest (String req)
{
    String[] list = req.split(",");
    String user = list[0];
    float x = Float.parseFloat(list[1]);
    float y = Float.parseFloat(list[2]);
    float z = Float.parseFloat(list[3]);
    float rx = Float.parseFloat(list[4]);
    float ry = Float.parseFloat(list[5]);
    float rz = Float.parseFloat(list[6]);

    return new Player(x, y, z, rx, ry, rz, user);
}
}

It's hard to reproduce this with missing classes. Can you edit the question and remove/add references/classes that you are not including here? — ernest_k
– ernest_k, Commented Mar 31, 2018 at 8:33
'Won't actually send' is not a problem description. You should not close the buffered reader before sending the response. — user207421
– user207421, Commented Mar 31, 2018 at 9:02
I just tried your code, and only built a custom client and an empty Player-class. It works just fine. How are you sending data from the client to your server? — Kristin
– Kristin, Commented Mar 31, 2018 at 9:03
@eli Don't know how you managed that. It should throw SocketException: socket closed at os.writeBytes(response). — user207421
– user207421, Commented Mar 31, 2018 at 9:41
I moved the close-call, of course. Edit: no I didn't... strange. But it does indeed read a line from a client correctly. No response is sent, though (wasn't checking for it before now). — Kristin
– Kristin, Commented Mar 31, 2018 at 9:42

user207421 · Accepted Answer · 2018-04-01 23:46:01Z

1

This code will throw SocketException: Socket closed because of br.close(), but assuming you've removed that, I suggest that your client is reading lines but you aren't sending lines. Add a line terminator to the message, or use BufferedWriter.newLine().

edited Apr 1, 2018 at 23:46

answered Mar 31, 2018 at 15:06

user207421

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