recvmsg() function of python socket class

Overview:

The recvmsg() function receives messages through TCP sockets, UDP sockets and Unix domain sockets.
The recvmsg() function returns a tuple consisting of data received from the socket, ancillary data(i.e., control information), flags associated with the data and the address of the sender.
The Berkeley sockets implementation has the recvmsg() function receive data into multiple buffers. The Python implementation of recvmsg_into() function receives data into multiple buffers. The recvmsg() function returns the received message as a bytes object in a tuple along with other message related information.
The recvmsg() is versatile that it works with TCP sockets, UDP sockets and Unix domain sockets.

Example - Multi-threaded TCP server:

# A Python TCP server program that waits
# and serves a text string to the clients
# connected to it using the socket methods
# recvmsg() and sendmsg()
import socket
import threading

# Function that creates a server socket and
# makes it to listen at a specific port for
# incoming connections
def serverInit():
tcpServer = socket.socket()
ipAddress = "127.0.0.1"
portNum = 34000

# Bind to ip and port
tcpServer.bind((ipAddress, portNum))
print("TCP server listening at IP address {} port {}".format(ipAddress, portNum))

# Start listening
tcpServer.listen()
return tcpServer

# Function that processes requests from clients
# and sends responses - used as the target function of
# threads spawned for each request
def processRequest(con, address):
while(True):
response = con.recvmsg(1024)
print(response[0])

msgs = []
if(response[0] != b''):
msg1 = "Read client message\n"
msg1Bytes = str.encode(msg1)
msgs.append(msg1Bytes)

msg2 = "Connection being closed"
msg2Bytes = str.encode(msg2)
msgs.append(msg2Bytes)

con.sendmsg(msgs)

con.close()
print("Connection closed")

break

# Start the server
clientConthreads = []
svr = serverInit()
while(True):
# Accept connections
(cltConnection, cltAddress) = svr.accept()

# Process requests
cltConThread = threading.Thread(target=processRequest, args=(cltConnection, cltAddress))

cltConThread.start()
clientConthreads.append(cltConThread)
for t in clientConthreads:
t.join()

Output:

TCP server listening at IP address 127.0.0.1 port 34000

b'GET / HTTP/1.1\r\nHost: localhost\r\n Connection: close\r\n\r\n'

Connection closed

Example - TCP client:

# Example Python program that connects to a TCP server
# and sends a request and prints the response of the server
# onto the console

import socket

# Create a TCP socket
sock = socket.socket()
sock.connect(("localhost", 34000))
print("Connected to the localhost")

httpGet = "GET / HTTP/1.1\r\nHost: localhost\r\n Connection: close\r\n\r\n"
reqBytes = str.encode(httpGet)
buffers = []
buffers.append(reqBytes)
sock.sendmsg(buffers)

while(True):
   response = sock.recvmsg(1024)
   print(response[0])
   if response[0] != b'':
       sock.close()
       break

print("Connection closed")

Output:

Connected to the localhost

b'Read client message\nConnection being closed'

Connection closed

Recvmsg() function of python socket class

Overview:

Example - Multi-threaded TCP server:

Output:

Example - TCP client:

Output: