Implement server and client classes

src/main/java/com/university/chat/Server/ChatServer.java

@@ -1,15 +1,31 @@
 package com.university.chat.Server;
 
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+
 public class ChatServer {
-    // TODO: declare a single shared UserManager instance (static final)
-    //         This MUST be shared by all ClientSession threads so that
-    //         broadcasting and private messaging work correctly.
+    public static final UserManager userManager = new UserManager();
+    public static ServerSocket serverSocket;
 
     public static void main(String[] args) {
-        // TODO: Create a ServerSocket
+        try {
+            serverSocket = new ServerSocket(555);
+        } catch (IOException e){
+            throw new RuntimeException(e);
+        }
+
+        while(true){
+            try {
+                Socket socket = serverSocket.accept();
+                System.out.println("New client accepted.");
+
+                ClientSession session = new ClientSession(socket, userManager);
+                new Thread(session).start();
+            } catch(IOException e){
+                System.err.println("Cannot establish connection");
+            }
+        }
 
-        // TODO: In an infinite loop:
-        //  accept an incoming client connection
-        //  make a new thread running ClientSession for each user.
     }
 }