✔ Serversocket und Server, Probleme mit Datenausgabe bei mehreren Clienten.

package test;

import java.io.BufferedReader;
import java.io.BufferedWriter;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.OutputStreamWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;

public class ChatServer {

	private static String back = "";
	private static ArrayList<String> socketList = new ArrayList<String>();

	private static void handleConnection(Socket client) throws IOException {
		String lineSeparator = System.getProperty("line.separator");
		BufferedReader in = new BufferedReader(new InputStreamReader(
				client.getInputStream()));
		in.ready();
		String read2 = "";
		String read = null;
		while ((read = in.readLine()) != null) {

			read = read + lineSeparator;
			read2 = read2 + read;

		}
		back = read2;

		output();
	}

	public static void main(String[] args) throws IOException {
		ServerSocket server = new ServerSocket(3141, 30,
				InetAddress.getLocalHost());
		ServerInput si = new ServerInput(socketList);
		Thread t = new Thread(si);
		t.start();
		while (true) {
			Socket client = null;

			try {

				client = server.accept();
				handleConnection(client);
			} catch (IOException e) {
				e.printStackTrace();
			} finally {
				if (client != null)
					try {
						client.close();
					} catch (IOException e) {
					}
			}
		}
	}

	public static void output() {
		Socket server = null;
		try {
			for (int count = 0; count < socketList.size(); count++) {
				String b = socketList.get(count);
				server = new Socket(b, 3143);
				BufferedWriter out = new BufferedWriter(new OutputStreamWriter(
						server.getOutputStream()));

				out.write(back, 0, back.length());
				out.flush();
			}
		} catch (IOException e) {
		} finally {
			if (server != null)
				try {
					server.close();
				} catch (IOException e) {
				}
		}
	}
}

package test;

import java.io.BufferedWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.net.InetAddress;
import java.net.ServerSocket;
import java.net.Socket;
import java.util.ArrayList;

public class ServerInput implements Runnable {

	private ArrayList<String> socketList;
	public ServerInput(ArrayList<String> socketList2) {
		socketList = socketList2;
	}

	private void handleConnection(Socket client) throws IOException {
		int count = 0;
		for (int counti = 0; counti < socketList.size(); counti++) {
			if (client.getInetAddress().equals(socketList.get(counti))) {
				count = 1;
			}
		}
		if (count == 0) {
			 socketList.add(client.getInetAddress().getHostAddress());
		} else {

			BufferedWriter out = new BufferedWriter(new OutputStreamWriter(
					client.getOutputStream()));
			String s = "Es darf nur ein Fenster geöffnet werden!";
			out.write(s, 0, s.length());
			out.flush();
			client.close();
		}

	}

	@Override
	public void run() {
		ServerSocket server;
		try {
			server = new ServerSocket(3140, 30, InetAddress.getLocalHost());

			while (true) {
				Socket client = null;

				try {
					client = server.accept();
					handleConnection(client);
				} catch (IOException e) {
					e.printStackTrace();
				} finally {
					if (client != null)
						try {
							client.close();
						} catch (IOException e) {
						}
				}
			}
		} catch (IOException e1) {
		}

	}
}