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POPython client-server script hangs until I press [enter]
 

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  1. POPython client-server script hangs until I press [enter]
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    <p>I have a basic client-server script in Python using sockets. The server binds to a specific port and waits for a client connection. When a client connects, they are presented with a raw_input prompt that sends the entered commands to a subproc on the server and pipes the output back to the client. Sometimes when I execute commands from the client, the output will hang and not present me with the raw_input prompt until I press the [enter] key. At first I thought this might have been a buffer problem but it happens when I use commands with a small output, like 'clear' or 'ls', etc.</p> <p>The client code:</p> <pre><code>import os, sys import socket from base64 import * import time try: HOST = sys.argv[1] PORT = int(sys.argv[2]) except IndexError: print("You must specify a host IP address and port number!") print("usage: ./handler_client.py 192.168.1.4 4444") sys.exit() socksize = 4096 server = socket.socket(socket.AF_INET, socket.SOCK_STREAM) try: server.connect((HOST, PORT)) print("[+] Connection established!") print("[+] Type ':help' to view commands.") except: print("[!] Connection error!") sys.exit(2) while True: data = server.recv(socksize) cmd = raw_input(data) server.sendall(str(cmd)) server.close() </code></pre> <p>Server code:</p> <pre><code>import os,sys import socket import time from subprocess import Popen,PIPE,STDOUT,call HOST = '' PORT = 4444 socksize = 4096 activePID = [] conn = socket.socket(socket.AF_INET, socket.SOCK_STREAM) conn.bind((HOST, PORT)) conn.listen(5) print("Listening on TCP port %s" % PORT) def reaper(): while activePID: pid,stat = os.waitpid(0, os.WNOHANG) if not pid: break activePID.remove(pid) def handler(connection): time.sleep(3) while True: cmd = connection.recv(socksize) proc = Popen(cmd, shell=True, stdout=PIPE, stderr=PIPE, stdin=PIPE, ) stdout, stderr = proc.communicate() if cmd == ":killme": connection.close() sys.exit(0) elif proc: connection.send( stdout ) connection.send("\nshell =&gt; ") connection.close() os._exit(0) def accept(): while 1: global connection connection, address = conn.accept() print "[!] New connection!" connection.send("\nshell =&gt; ") reaper() childPid = os.fork() # forks the incoming connection and sends to conn handler if childPid == 0: handler(connection) else: activePID.append(childPid) accept() </code></pre>
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    1. USohdae
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    1. COThe question is what am I missing here? It seems that the client should be able to transition from printing output to the shell prompt rather seemlessly. Any thoughts?
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      1. POPython client-server script hangs until I press [enter]
      1. USohdae
    2. COYou might want to check out [argparse](http://docs.python.org/library/argparse.html#module-argparse) for command line arguments - when it's as simple as your code currently is, it's not really needed, but if it gets more complex, it's worth a look.
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    3. COThe entire code is a good bit more complex than that actually, this is just a client server snippets. I just shuffled it around a bit so my examples weren't 5 pages long. Thank you for the advice though :)
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