Server-Server Discovery

client.py

@@ -65,6 +65,26 @@ class Client():
             except socket.timeout:
                 pass
 
+    def discover_group_members(self):
+        # Send a broadcast message to discover group members
+        group_discovery_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        group_discovery_socket.settimeout(3)  # Set timeout to 3 seconds
+        group_discovery_socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+        group_discovery_socket.sendto(str.encode("Any group members here?"), ('<broadcast>', BROADCAST_PORT))
+
+        try:
+            while True:
+                data, addr = group_discovery_socket.recvfrom(1024)
+                if data:
+                    group_member_IP = data.decode()
+                    if group_member_IP != MY_IP and group_member_IP not in self.group_members:
+                        self.group_members[group_member_IP] = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
+                        self.printwt(f'New group member found: {group_member_IP}')
+                        # Respond to the new member with own IP
+                        group_discovery_socket.sendto(str.encode(MY_IP), (group_member_IP, BROADCAST_PORT))
+        except socket.timeout:
+            group_discovery_socket.close()
+
     def receive_messages(self):
         while True:
             try:
@@ -82,6 +102,11 @@ class Client():
 if __name__ == "__main__":
     client = Client()
 
+    # Start a thread to discover group members
+    discovery_thread = threading.Thread(target=client.discover_group_members)
+    discovery_thread.start()
+
+    # Start the thread to send and receive messages
     thread1 = threading.Thread(target = client.BroadcastSendAndReceive)
     thread1.start()
     thread1.join()
\ No newline at end of file

server.py

 import socket
 import threading
 from datetime import datetime
+import time
 
 # Listening port
 BROADCAST_PORT = 5973
@@ -11,13 +12,22 @@ MY_IP = socket.gethostbyname(MY_HOST)
 
 class Server():
     def __init__(self):
+        self.group_members = {}  # Dictionary to store group members with their IPs as keys
         self.leader_IP = '' # fix the leader IP
         self.clients = []
 
+
     def printwt(self, msg):
         current_date_time = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
         print(f'[{current_date_time}] {msg}')
 
+
+    def print_group_members(self):
+        self.printwt("Current group members:")
+        for member, timestamp in self.group_members.items():
+            self.printwt(f'{member} (joined at {timestamp})')
+
+
     # Listen to client broadcast (request) and reply with Server IP
     def ListenForClientAndReply(self):
         # Create a UDP socket
@@ -38,12 +48,12 @@ class Server():
                 self.printwt(data.decode())
 
         # if Iam the leader, answer the client including my IP
-                # if MY_IP == self.leader_IP:
-                if data:
+                if MY_IP == self.leader_IP:
                     reply_message = MY_IP
                     listen_socket.sendto(str.encode(reply_message), addr)
                     self.printwt('Replied my IP to new client')
 
+
     def handle_client(self, client_socket, client_address):
         self.clients.append(client_socket)
 
@@ -58,6 +68,7 @@ class Server():
                 self.clients.remove(client_socket)
                 break
 
+
     def broadcast(self, message, sender_socket):
         for client in self.clients:
             try:
@@ -67,13 +78,44 @@ class Server():
                 self.clients.remove(client)
 
 
+    def announce_leader(self):
+        # Send a broadcast message to determine the leader
+        leader_broadcast_socket = socket.socket(socket.AF_INET, socket.SOCK_DGRAM)
+        leader_broadcast_socket.settimeout(3)  # Set timeout to 3 seconds
+        leader_broadcast_socket.setsockopt(socket.SOL_SOCKET, socket.SO_BROADCAST, 1)
+        leader_broadcast_socket.sendto(str.encode("Who is the leader?"), ('<broadcast>', BROADCAST_PORT))
+
+        try:
+            data, addr = leader_broadcast_socket.recvfrom(1024)
+            if data:
+                self.leader_IP = addr[0]
+                self.group_members[self.leader_IP] = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
+                self.printwt(f'Leader elected: {self.leader_IP}')
+       
+        except socket.timeout:
+            # If no response received, assume this server is the leader
+            self.leader_IP = MY_IP
+            self.group_members[self.leader_IP] = datetime.now().strftime('%Y-%m-%d %H:%M:%S')
+            self.printwt(f'I am the first server and leader: {self.leader_IP}')
+
+        leader_broadcast_socket.close()
+
 # starting all simultaneously working procedures
 if __name__== '__main__':
     server = Server()
 
+    # Start a thread to announce the leader
+    leader_thread = threading.Thread(target=server.announce_leader)
+    leader_thread.start()
+
+     # Start the thread to listen for client broadcasts
     thread1 = threading.Thread(target = server.ListenForClientAndReply)
     thread1.start()
 
+    # Start a thread to periodically print the group members
+    print_group_thread = threading.Thread(target=server.print_group_members)
+    print_group_thread.start()
+
     # Socket erstellen und binden
     server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
     server_socket.bind((MY_IP, 5555))