"""Script for Tkinter GUI chat client."""
from socket import AF_INET, socket, SOCK_STREAM
from threading import Thread
import tkinter

def receive():
    """Handles receiving of messages."""
    while True:
        try:
            msg = client_socket.recv(BUFSIZ).decode("utf8")
            msg_list.insert(tkinter.END, msg)
        except OSError:  # Possibly client has left the chat.
            break


def send(event=None):  # event is passed by binders.
    """Handles sending of messages."""
    msg = my_msg.get()
    my_msg.set("")  # Clears input field.
    client_socket.send(bytes(msg, "utf8"))
    if msg == "{quit}":
        client_socket.close()
        top.quit()



def on_closing(event=None):
    """This function is to be called when the window is closed."""
    my_msg.set("{quit}")
    send()


top = tkinter.Tk()
top.title("CS201")

messages_frame = tkinter.Frame(top)
my_msg = tkinter.StringVar()  # For the messages to be sent.
my_msg.set("Name")
scrollbar = tkinter.Scrollbar(messages_frame)  # To navigate through past messages.

msg_list = tkinter.Listbox(messages_frame, height=15, width=50, yscrollcommand=scrollbar.set)
scrollbar.pack(side=tkinter.RIGHT, fill=tkinter.Y)
msg_list.pack(side=tkinter.LEFT, fill=tkinter.BOTH)
msg_list.pack()
messages_frame.pack()

entry_field = tkinter.Entry(top, textvariable=my_msg)
entry_field.bind("<Return>", send)
entry_field.pack()
send_button = tkinter.Button(top, text="Send", command=send)
send_button.pack()
top.protocol("WM_DELETE_WINDOW", on_closing)

HOST = input('Enter host: ')
PORT = input('Enter port: ')
if not PORT:
    PORT = 33000  # Default value.
else:
    PORT = int(PORT)
BUFSIZ = 1024
ADDR = (HOST, PORT)
client_socket = socket(AF_INET, SOCK_STREAM)
client_socket.connect(ADDR)

receive_thread = Thread(target=receive)
receive_thread.start()
tkinter.mainloop()  # Starts GUI execution.












=============================== SERVER

#!/usr/local/bin/python3.6

"""Server for multithreaded (asynchronous) chat application."""
from socket import AF_INET, socket, SOCK_STREAM
from threading import Thread


def accept_incoming_connections():
    """Sets up handling for incoming clients."""
    while True:
        client, client_address = SERVER.accept()
        print("%s:%s has connected." % client_address)
        client.send(bytes("Greetings from the cave! Now type your name and press enter!", "utf8"))
        addresses[client] = client_address
        Thread(target=handle_client, args=(client,)).start()


def handle_client(client):  # Takes client socket as argument.
    """Handles a single client connection."""

    name = client.recv(BUFSIZ).decode("utf8")
    welcome = 'Welcome %s! If you ever want to quit, type {quit} to exit.' % name
    client.send(bytes(welcome, "utf8"))
    msg = "%s has joined the chat!" % name
    broadcast(bytes(msg, "utf8"))
    clients[client] = name

    while True:
        msg = client.recv(BUFSIZ)
        if msg != bytes("{quit}", "utf8"):
            broadcast(msg, name+": ")
        else:
            client.send(bytes("{quit}", "utf8"))
            client.close()
            del clients[client]
            broadcast(bytes("%s has left the chat." % name, "utf8"))
            break


def broadcast(msg, prefix=""):  # prefix is for name identification.
    """Broadcasts a message to all the clients."""

    for sock in clients:
        sock.send(bytes(prefix, "utf8")+msg)


clients = {}
addresses = {}

HOST = ''
PORT = 33000
BUFSIZ = 1024
ADDR = (HOST, PORT)

SERVER = socket(AF_INET, SOCK_STREAM)
SERVER.bind(ADDR)

if __name__ == "__main__":
    SERVER.listen(5)
    print("Waiting for connection...")
    ACCEPT_THREAD = Thread(target=accept_incoming_connections)
    ACCEPT_THREAD.start()
    ACCEPT_THREAD.join()
    SERVER.close()