CODEWITHSUNDEEP
javatcpclient-server
SpeedEX505
SpeedEX505

Reputation: 2076

TCP. client connects even if server doesn't accept him

I have TCP server-client application. It works but sometime something happens. Client connects to server but server says he doesn't accepted him.

Server side code:

while(!stopped){
            try {
                AcceptClient();
            } catch(SocketTimeoutException ex){
                continue;
            } catch (IOException ex) {
                System.err.println("AppServer: Client cannot be accepted.\n"+ex.getMessage()+"\n");
                break;
            }
...

private void AcceptClient() throws IOException {
    clientSocket = serverSocket.accept();
    clientSocket.setSoTimeout(200);
    out = new ObjectOutputStream(clientSocket.getOutputStream());
    in = new ObjectInputStream(clientSocket.getInputStream());
    System.out.println("Accepted connection from "+clientSocket.getInetAddress());
}

Client side code:

    try {
        socket = new Socket(IPAddress, serverPort);
        socket.setSoTimeout(5000);
        out = new ObjectOutputStream(socket.getOutputStream());
        in = new ObjectInputStream(socket.getInputStream());
    } catch (IOException e1) {
        sendSystemMessage("DISCONNECTED");
        sendSystemMessage(e1.getMessage());
        return;
    }
    sendSystemMessage("CONNECTED");

If client connects the message:

Accepted connection from ... appears. But sometimes it doesn't appear even if client sends message "CONNECTED"

Server is still runing the loop trying to get client and it is catching socketTimeoutException. Client is connected, sends message and waits for response.

Upvotes: 0

Views: 85

Answers (2)

SpeedEX505
SpeedEX505

Reputation: 2076

I found the problem. The communication on my net is too slow so it timeouts in getting inputstream. The solution has two parts. Flushing outputstream before getting inputstream. And set socket timout after streams are initialized.

serverside:

clientSocket = serverSocket.accept();
out = new ObjectOutputStream(clientSocket.getOutputStream());
out.flush()
in = new ObjectInputStream(clientSocket.getInputStream());
clientSocket.setSoTimeout(200);

Upvotes: 0

Pelit Mamani
Pelit Mamani

Reputation: 2381

I suspect a missing 'flush' inside your client's 'sendSystemMessage()'. Unfortunately the constructor of ObjectInputStream attempts to read a header from the underlying stream (which is not very intuitive IMHO). So if the client fails to flush the data - the server may remain stuck on the line "in = new ObjectInputStream(socket.getInputStream())"...

As a side note it's usually better for a server to launch a thread per incoming client, but that's just a side remark (plus it obviously depends on requirements).

Upvotes: 1

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