import socket, select, sys
from tkinter import *
 
def prompt(name) :
    log.insert(END, '<You> ')
 
host = 'localhost'
port = 5000
    
tk = Tk()
    
text = StringVar()
name = StringVar()
name.set('User')
text.set('')
tk.title('MegaChat')
tk.geometry('400x300')
log = Text(tk)
nick = Entry(tk, textvariable=name)
msg = Entry(tk, textvariable=text)
msg.pack(side='bottom', fill='x', expand='true')
nick.pack(side='bottom', fill='x', expand='true')
log.pack(side='top', fill='both',expand='true')
    
s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.settimeout(2)
     
# connect to remote host
try :
    s.connect((host, port))
except :
    log.insert(END, 'Unable to connect\n')
    #sys.exit()
     
log.insert(END, 'Connected to remote host. Start sending messages')
     
while 1:
    socket_list = [s]
         
    # Get the list sockets which are readable
    read_sockets, write_sockets, error_sockets = select.select(socket_list , [], [])
         
    for sock in read_sockets:
         #incoming message from remote server
         if sock == s:
             data = sock.recv(4096).decode()
             if not data :
                 log.insert(END, '\nDisconnected from chat server')
                 #sys.exit()
             else :
                 #print data
                 prompt()
                 log.insert(END, data)
             
         #user entered a message
         else:
            s.send(text.encode())
            #prompt()
#вот сюда он не доходит из-за бесконечного цикла выше              
tk.mainloop()

 import socket, select, string, sys
 
def prompt() :
    sys.stdout.write('<You> ')
    sys.stdout.flush()
 
#main function
if __name__ == "__main__":    
    host = 'localhost'
    port = 5000
     
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.settimeout(2)
     
    # connect to remote host
    try :
        s.connect((host, port))
    except :
        print('Unable to connect')
        sys.exit()
     
    print('Connected to remote host. Start sending messages')
    prompt()
     
    while 1:
        socket_list = [sys.stdin, s]
         
        # Get the list sockets which are readable
        read_sockets, write_sockets, error_sockets = select.select(socket_list , [], [])
         
        for sock in read_sockets:
            #incoming message from remote server
            if sock == s:
                data = sock.recv(4096).decode()
                if not data :
                    print('\nDisconnected from chat server')
                    sys.exit()
                else :
                    #print data
                    sys.stdout.write(data)
                    prompt()
             
            #user entered a message
            else :
                msg = sys.stdin.readline()
                s.send(msg.encode())
                prompt()