TCP死鎖：

兩個程序共享有限的資源，由於糟糕的計劃，A程序只能等待B程序資源占用結束後才能使用資源，這種情況就是死鎖（deadlock）

代碼的解釋明天給出

#!/usr/bin/env python3
#-*- encoding:utf8 -*-

import argparse,sys,socket

def server(host,port,bytecount):
    sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    sock.setsockopt(socket.SOL_SOCKET,socket.SO_REUSEADDR,
 
1)
    sock.bind((host,port))
    sock.listen(5)
    print("listening at",sock.getsockname())

    while True:
        sc,addr = sock.accept()
        print("Processing up to 1024 Bytes at a time from",addr)

        n = 0
        while True:
            data = sc.recv(1024)
            if not data:break
 

            output = data.decode().upper().encode()
            sc.sendall(output)
            n += len(data)
            print("\r %d Bytes process so far" %(n,),end=‘‘)
            sys.stdout.flush()
        sc.close()
        print("socket closed")

def client(host,port,bytecount):
    sock = socket.socket(socket.AF_INET,socket.SOCK_STREAM)
    bytecount 
 
= (bytecount+15) // 16 * 16
    message = ("capitalize this!").encode()

    print("sending",bytecount,"bytes of data , in chunks of 16 bytes")
    sock.connect((host,port))

    sent = 0
    while sent < bytecount:
        sock.sendall(message)
        sent+= len(message)
        print("\r %d Bytes sent" %(sent,),end=‘‘)
        sys.stdout.flush()
    print()
    sock.shutdown(socket.SHUT_WR)

    print(‘receiving all the data the server sends back‘)

    received = 0

    while True:
        data = sock.recv(42)
        if not received:print(‘The first data received says‘,repr(data))
        if not data:break
        received += len(data)
        print(‘\r %d Bytes received‘ %(received,),end=‘‘)
    print()
    sock.close()


if __name__ == "__main__":
    choices = {
        "client":client,
        "server":server
    }
    parser = argparse.ArgumentParser(description=‘Get deadlocked over TCP‘)
    parser.add_argument(‘role‘,choices=choices,help=‘which role to play‘)
    parser.add_argument(‘host‘,help=‘interface the server listen it;‘‘host the client to send‘)
    parser.add_argument(‘bytecount‘, type = int , nargs = "?" , default=16 , help=‘number of bytes for cleint to send (default 16)‘)
    parser.add_argument(‘-p‘, metavar=‘PORT‘ ,type=int , default=1060 , help=‘TCP PORT(default 1060)‘)

    args = parser.parse_args()
    function=choices[args.role]
    function(args.host, args.p , args.bytecount)

TCP死鎖演示