CODEWITHSUNDEEP
javamultithreadingnetwork-programmingtcp
BleedObsidian
BleedObsidian

Reputation: 45

Java TCP Multi-thread issue

My program works fine and many users can connect and send commands to the server. But when a user spams the server with commands the server blocks out all other clients and the server doesn't receive messages from clients other than the one that spammed. Why is this?

TCPAccept Connections

    package game.server;

import java.io.IOException;
import java.net.Socket;

public class TCPAcceptConnections implements Runnable
{
    public static Socket clientSocket = null;;
    int clientID = -1;

    public void run()
    {
        while(Main.TCP)
        {
            try
            {
                clientSocket = TCPServer.serverSocket.accept();
                System.out.println("Client Connected.");
                clientID++;

                new TCPClientManager(clientSocket, clientID).run();
            } 
            catch (IOException e)
            {
                System.out.println("Couldn't create client socket.");
                System.exit(-1);
            }
        }
    }
}

TCPClientManager:

    package game.server;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.PrintWriter;
import java.net.Socket;

public class TCPClientManager implements Runnable
{
    Socket client;

    int clientID;

    static PrintWriter out;
    static BufferedReader in;
    String inputLine, outputLine;

    boolean destroy = false;

    public TCPClientManager(Socket cs, int id)
    {
        try
        {
            client = cs;
            clientID = id;
            out = new PrintWriter(client.getOutputStream(), true);
            in = new BufferedReader(new InputStreamReader(client.getInputStream()));
        } catch(IOException e)
        {
            e.printStackTrace();
        }
    }

    public void run()
    {
        System.out.println("Created TCPManager for client.");
        String command;

        while(!destroy)
        {
            try
            {
                if((command = in.readLine()) != null) //If received something
                {
                    System.out.println("Commad received: " + command);
                        System.out.println(" " + Commands.proccessCommand(command));
                    System.out.println("Command proccessed");
                }
                else
                {
                    client.close();
                    destroy = true;
                }
            } catch (IOException e)
            {
                try
                {
                    client.close();
                } catch (IOException e1)
                {
                    e1.printStackTrace();
                    destroy = true;
                }
                System.out.println("Client lost connection.");
                destroy = true;
            }
        }
        System.out.println("TCPManager for client destroyed.");
    }
}

Commands:

package game.server;

public class Commands
{
    public static String proccessCommand(String command)
    {
        if(command.equalsIgnoreCase("cp"))
        {
            System.out.println("Creating player...");
                System.out.println("    Retrieved client");
            return "Player Created";
        }
        else
        {
            return "Unkown command: " + command;
        }
    }
}

Upvotes: 1

Views: 830

Answers (1)

user207421
user207421

Reputation: 310911

If you get an unknown command, you should log it and close the connection.

But you have a more severe problem. You aren't stopping the client handler when it reads null. So once a client disconnects the read will spin futilely forever. If readLine() returns null you must close the socket and exit the loop. If you get any IOException you must also close the socket.

Upvotes: 1

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