server.py

import socketserver, threading
from socket import AF_INET6
dictionary = {}
fail = b"error\n"
class CryptoChatHandler(socketserver.BaseRequestHandler):
    def handle(self):
        global dictionary
        data = self.request[0]
        socket = self.request[1];
        if(data.startswith(b"add")):
            if (self.client_address[0], self.client_address[1]) in dictionary:
                socket.sendto(b"already exists\n", self.client_address);
            else:
                try:
                    username = data[4:]
                    if(username[-1] == 10):
                        username = username[:-1]
                    values = list(dictionary.values())
                    if(username in values):
                        socket.sendto(b"username exists\n", self.client_address);
                    else:
                        dictionary[(self.client_address[0], self.client_address[1])] = username
                        socket.sendto(b"success\n", self.client_address);
                except IndexError:
                    socket.sendto(b"syntax error\n", self.client_address);
        elif(data.startswith(b"kickme")):
            try:
                del dictionary[(self.client_address[0], self.client_address[1])]
                socket.sendto(b"success\n", self.client_address);
            except KeyError:
                socket.sendto(b"nonexistent\n", self.client_address);
        elif(data.startswith(b"ls")):
            l = []
            for key in dictionary:
                s = str(key[0]) + "," + str(key[1])+":"
                s = s.encode()
                s = s + dictionary[key]
                l.append(s);
            l = b"\n".join(l) + b"\n"
            socket.sendto(l, self.client_address);
        elif(data.startswith(b"req")):
            try:
                username = data[4:]
                if(username[-1] == 10):
                    username = username[:-1]
                addr = False
                keys = list(dictionary.keys())
                values = list(dictionary.values())
                i = 0;
                v = -86;
                while i < len(values):
                    if values[i] == username:
                        v = i
                        break
                    i = i + 1
                if(v != -86 and keys[v] == (self.client_address[0], self.client_address[1])):
                    socket.sendto(b"That is you\n", self.client_address);
                elif(v != -86):
                    addr = keys[v]
                    a = "address " + addr[0]+","+str(addr[1])+"\n"
                    a = a.encode()
                    msg = b"request-from " + self.client_address[0].encode() + b"," + str(self.client_address[1]).encode() + b"\n"
                    socket.sendto(msg, (addr[0], addr[1]))
                    socket.sendto(a, self.client_address)
                else:
                    socket.sendto(b"Not Found\n", self.client_address)
            except IndexError:
                socket.sendto(b"syntax error\n", self.client_address)
        else:
            if(data == 10):
                socket.sendto(b'\n', self.client_address);
            else:
                socket.sendto(fail, self.client_address);
class CryptoChatServer(socketserver.ThreadingMixIn, socketserver.UDPServer):
    address_family = AF_INET6
    daemon_threads = True
    allow_reuse_address = True
if __name__ == "__main__":
    HOST, PORT = "::", 6666
    server = CryptoChatServer((HOST, PORT), CryptoChatHandler);
    server.serve_forever();