fixes #20

server/src/main/java/ch/zhaw/pm2/multichat/server/Server.java

@@ -6,6 +6,8 @@ import java.io.IOException;
 import java.net.SocketException;
 import java.util.HashMap;
 import java.util.Map;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
 
 
 public class Server {
@@ -62,23 +64,34 @@ public class Server {
     }
 
     private void start() {
+        ReentrantLock mutex = new ReentrantLock();
+        Condition nameComplete = mutex.newCondition();
         System.out.println("Server started.");
         try {
             while (true) {
                  NetworkHandler.NetworkConnection<String> connection = networkServer.waitForConnection();
-                 ServerConnectionHandler connectionHandler = new ServerConnectionHandler(connection, connections);
+                 ServerConnectionHandler connectionHandler = new ServerConnectionHandler(connection, connections, mutex, nameComplete);
                  new Thread(connectionHandler).start();
+                 mutex.lock();
+                 try {
+                     nameComplete.await();
                      System.out.println(String.format("Connected new Client %s with IP:Port <%s:%d>",
                              connectionHandler.getUserName(),
                              connection.getRemoteHost(),
                              connection.getRemotePort()
                      ));
                  }
+                finally {
+                     mutex.unlock();
+                 }
+            }
         } catch(SocketException e) {
             System.out.println("Server connection terminated");
         }
         catch (IOException e) {
             System.err.println("Communication error " + e);
+        } catch (InterruptedException e) {
+            throw new RuntimeException(e);
         }
         // close server
         System.out.println("Server Stopped.");

server/src/main/java/ch/zhaw/pm2/multichat/server/ServerConnectionHandler.java

@@ -11,6 +11,8 @@ import java.util.Map;
 import java.util.Objects;
 import java.util.Scanner;
 import java.util.concurrent.atomic.AtomicInteger;
+import java.util.concurrent.locks.Condition;
+import java.util.concurrent.locks.ReentrantLock;
 
 import static ch.zhaw.pm2.multichat.server.ServerConnectionHandler.State.*;
 
@@ -30,6 +32,10 @@ public class ServerConnectionHandler implements Runnable{
     private static final String USER_NONE = "";
     private static final String USER_ALL = "*";
 
+    private ReentrantLock mutex;
+
+    private Condition nameComplete;
+
     private String userName = "Anonymous-"+connectionId;
     private State state = NEW;
 
@@ -43,11 +49,13 @@ public class ServerConnectionHandler implements Runnable{
     }
 
     public ServerConnectionHandler(NetworkHandler.NetworkConnection<String> connection,
-                                   Map<String,ServerConnectionHandler> registry) {
+                                   Map<String,ServerConnectionHandler> registry, ReentrantLock mutex, Condition nameComplete) {
         Objects.requireNonNull(connection, "Connection must not be null");
         Objects.requireNonNull(registry, "Registry must not be null");
         this.connection = connection;
         this.connectionRegistry = registry;
+        this.mutex = mutex;
+        this.nameComplete = nameComplete;
     }
 
     public String getUserName() {
@@ -71,12 +79,13 @@ public class ServerConnectionHandler implements Runnable{
                 System.out.println("Connection terminated by remote");
                 connectionRegistry.remove(userName);
                 System.out.println("Unregistered because client connection terminated: " + userName + " " + e.getMessage());
-        } catch(IOException e) {
+            } catch (IOException e) {
                 System.err.println("Communication error: " + e);
-        } catch(ClassNotFoundException e) {
+            } catch (ClassNotFoundException e) {
                 System.err.println("Received object of unknown type: " + e.getMessage());
             }
             System.out.println("Stopping Connection Handler for " + userName);
+
     }
 
     public void stopReceiving() {
@@ -124,7 +133,14 @@ public class ServerConnectionHandler implements Runnable{
                 if (sender == null || sender.isBlank()) sender = this.userName;
                 if (connectionRegistry.containsKey(sender))
                     throw new ChatProtocolException("User name already taken: " + sender);
+                mutex.lock();
+                try {
                     this.userName = sender;
+                    nameComplete.signal();
+                }
+                finally {
+                    mutex.unlock();
+                }
                 connectionRegistry.put(userName, this);
                 sendData(USER_NONE, userName, DATA_TYPE_CONFIRM, "Registration successfull for " + userName);
                 this.state = CONNECTED;