Python Socket Listening

Question

All of the below mentioned is on windows machines using python 2.7

Hello,

I am currently attempting to listen on a socket for data send by a

Answer 1

If your in Python 3 by now and still wondering about sockets, here's a basic way of using them:

server.py

import time
import socket

# creating a socket object
s = socket.socket(socket.AF_INET,
                  socket.SOCK_STREAM)

# get local Host machine name
host = socket.gethostname() # or just use (host == '')
port = 9999

# bind to pot
s.bind((host, port))

# Que up to 5 requests
s.listen(5)

while True:
    # establish connection
    clientSocket, addr = s.accept()
    print("got a connection from %s" % str(addr))
    currentTime = time.ctime(time.time()) + "\r\n"
    clientSocket.send(currentTime.encode('ascii'))
    clientSocket.close()

client.py

import socket

# creates socket object
s = socket.socket(socket.AF_INET,
                  socket.SOCK_STREAM)

host = socket.gethostname() # or just use (host = '')
port = 9999

s.connect((host, port))

tm = s.recv(1024) # msg can only be 1024 bytes long

s.close()
print("the time we got from the server is %s" % tm.decode('ascii'))

Run server.py first, then run client.py

This is just receive and send the currentTime.

What's new in Python 3.4 sockets?

A major difference between python 2.7 sockets and python 3.4 sockets is the sending messages. you have to .encode() (usually using 'ascii' or blank as parameters/arguments) and then using .decode()

For example use .encode() to send, and use .decode() to receive.

Extra info: client/server socket tutorial

Answer 2

Playing around with this for a while finally got it working nice with a telnet session locally using python 2.7.

What it does is it sets up a thread that runs when the client connects listening for client stuff.

When the client sends a return ("\r\n" might have to change that if your interacting with a Linux system?) the message gets printed to the server, while this is happening if there is a raw input at the server side this will get sent to the client:

import socket
import threading
host = ''
port = 50000
connectionSevered=0

class client(threading.Thread):
    def __init__(self, conn):
        super(client, self).__init__()
        self.conn = conn
        self.data = ""
    def run(self):
        while True:
            self.data = self.data + self.conn.recv(1024)
            if self.data.endswith(u"\r\n"):
                print self.data
                self.data = ""

    def send_msg(self,msg):
        self.conn.send(msg)

    def close(self):
        self.conn.close()

try:
    s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
    s.bind((host,port))
    s.listen(5)
except socket.error:
    print 'Failed to create socket'
    sys.exit()

print '[+] Listening for connections on port: {0}'.format(port)


conn, address = s.accept()
c = client(conn)
c.start()
print '[+] Client connected: {0}'.format(address[0])
c.send_msg(u"\r\n")
print "connectionSevered:{0}".format(connectionSevered) 
while (connectionSevered==0):
    try:
        response = raw_input()  
        c.send_msg(response + u"\r\n")
    except:
        c.close()

The above answer will not work for more than a single connection. I have updated it by adding another thread for taking connections. It it now possible to have more than a single user connect.

import socket
import threading
import sys
host = ''
port = 50000

class client(threading.Thread):
    def __init__(self, conn):
        super(client, self).__init__()
        self.conn = conn
        self.data = ""

    def run(self):
        while True:
            self.data = self.data + self.conn.recv(1024)
            if self.data.endswith(u"\r\n"):
                print self.data
                self.data = ""

    def send_msg(self,msg):
        self.conn.send(msg)

    def close(self):
        self.conn.close()

class connectionThread(threading.Thread):
    def __init__(self, host, port):
        super(connectionThread, self).__init__()
        try:
            self.s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
            self.s.bind((host,port))
            self.s.listen(5)
        except socket.error:
            print 'Failed to create socket'
            sys.exit()
        self.clients = []

    def run(self):
        while True:
            conn, address = self.s.accept()
            c = client(conn)
            c.start()
            c.send_msg(u"\r\n")
            self.clients.append(c)
            print '[+] Client connected: {0}'.format(address[0])



def main():
    get_conns = connectionThread(host, port)
    get_conns.start()
    while True:
        try:
            response = raw_input() 
            for c in get_conns.clients:
                c.send_msg(response + u"\r\n")
        except KeyboardInterrupt:
            sys.exit()

if __name__ == '__main__':
    main()

Clients are not able to see what other clients say, messages from the server will be sent to all clients. I will leave that as an exercise for the reader.