💡 Fun Fact: The first chat system (Talkomatic) was created in 1973 at the University of Illinois - modern TCP chat rooms use similar concepts but with encryption and proxy capabilities!
Core Components
1. Chat Server
Handles client connections, message routing, and room management using TCP sockets
2. Telnet Proxy
Legacy interface allowing telnet clients to connect to modern chat systems
3. Client Apps
Native/GUI clients and terminal-based interfaces
TCP Chat Server Implementation (Python)
# chat_server.py
import socket
import threading
from collections import defaultdict
class ChatServer:
def __init__(self, host='0.0.0.0', port=5555):
self.clients = defaultdict(dict) # {room: {client_socket: username}}
self.server_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.server_socket.bind((host, port))
self.server_socket.listen(5)
print(f"🚀 Server listening on {host}:{port}")
def broadcast(self, message, room, sender_socket=None):
"""Send message to all clients in a room"""
for client in self.clients[room]:
if client != sender_socket: # Don't echo to sender
try:
client.send(message.encode('utf-8'))
except:
self.remove_client(client, room)
def handle_client(self, client_socket, room):
"""Manage individual client connections"""
username = client_socket.recv(1024).decode('utf-8')
self.clients[room][client_socket] = username
self.broadcast(f"🌟 {username} joined the room!", room)
while True:
try:
message = client_socket.recv(1024).decode('utf-8')
if not message:
break
formatted_msg = f"{username}: {message}"
self.broadcast(formatted_msg, room, client_socket)
except:
break
self.remove_client(client_socket, room)
def remove_client(self, client_socket, room):
"""Clean up disconnected clients"""
if client_socket in self.clients[room]:
username = self.clients[room][client_socket]
del self.clients[room][client_socket]
self.broadcast(f"👋 {username} left the room", room)
client_socket.close()
def run(self):
"""Main server loop"""
while True:
client_socket, addr = self.server_socket.accept()
room = client_socket.recv(1024).decode('utf-8') # First message is room name
threading.Thread(
target=self.handle_client,
args=(client_socket, room)
).start()
if __name__ == "__main__":
server = ChatServer()
server.run()
Telnet Proxy Gateway
# telnet_proxy.py
import socket
import threading
import re
class TelnetProxy:
def __init__(self, chat_host='localhost', chat_port=5555, proxy_port=2323):
self.chat_host = chat_host
self.chat_port = chat_port
self.proxy_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
self.proxy_socket.bind(('0.0.0.0', proxy_port))
self.proxy_socket.listen(5)
print(f"🔌 Telnet proxy running on port {proxy_port}")
def translate_telnet(self, telnet_socket):
"""Convert telnet raw commands to chat protocol"""
# Connect to real chat server
chat_socket = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
chat_socket.connect((self.chat_host, self.chat_port))
# Telnet negotiation stripping
telnet_socket.send(b"Welcome to Telnet Chat Proxy!\r\n")
telnet_socket.send(b"Enter room name: ")
room = telnet_socket.recv(1024).decode('ascii').strip()
chat_socket.send(room.encode('utf-8'))
telnet_socket.send(b"Enter username: ")
username = telnet_socket.recv(1024).decode('ascii').strip()
chat_socket.send(username.encode('utf-8'))
# Bidirectional forwarding
while True:
try:
# Telnet -> Chat Server
telnet_data = telnet_socket.recv(1024)
if not telnet_data: break
clean_data = re.sub(rb'\xFF[\xFB\xFC\xFD\xFE].', b'', telnet_data) # Strip telnet commands
chat_socket.send(clean_data.strip())
# Chat Server -> Telnet
chat_data = chat_socket.recv(1024)
if not chat_data: break
telnet_socket.send(chat_data + b'\r\n')
except:
break
telnet_socket.close()
chat_socket.close()
def run(self):
while True:
client, addr = self.proxy_socket.accept()
print(f"Telnet connection from {addr}")
threading.Thread(target=self.translate_telnet, args=(client,)).start()
Key Features
| Feature | Implementation | Security Consideration |
|---|---|---|
| Multi-room Support | Dictionary mapping rooms to client lists | Limit rooms per IP to prevent abuse |
| Telnet Compatibility | Command stripping and CRLF conversion | Sanitize telnet control sequences |
| Message Broadcasting | Selective echo to room members | Rate limiting per client |
| Connection Handling | Thread-per-client model | Max connections limit |
Advanced Enhancements
🔒 TLS Encryption
Wrap sockets with SSLContext for secure communication:
context = ssl.create_default_context(ssl.Purpose.CLIENT_AUTH)
🌐 WebSocket Gateway
Add browser support with WebSocket-to-TCP bridge:
async def websocket_handler(ws):
tcp_socket = connect_to_chat_server()
📊 Message Persistence
Store chat history in SQLite:
INSERT INTO messages VALUES (?,?,?,datetime('now'))
⚠️ Security Checklist
- Implement message size limits (prevent DoS)
- Add authentication for sensitive rooms
- Log all connection attempts
- Use non-blocking sockets for production
- Consider switching to asyncio for scale
Testing Your Chat System
Terminal Client
$ nc localhost 5555
general
Alice
Hello world!
^C
general
Alice
Hello world!
^C
Telnet Session
$ telnet localhost 2323
Welcome to Telnet Chat Proxy!
Enter room name: general
Enter username: Bob
Hi Alice!
Connection closed
Welcome to Telnet Chat Proxy!
Enter room name: general
Enter username: Bob
Hi Alice!
Connection closed