TCPIPserverTest.py

You can view and download this file on Github: TCPIPserverTest.py

#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
# This is an EXUDYN example
#
# Details:  Example for connecting two Python codes via TCP/IP
#           See file TCPIPclientTest.py for running on the other Python instance
#
# Author:   Johannes Gerstmayr
# Date:     2021-11-06
#
# Copyright:This file is part of Exudyn. Exudyn is free software. You can redistribute it and/or modify it under the terms of the Exudyn license. See 'LICENSE.txt' for more details.
#
#+++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++

import socket
import sys
import time
import struct

#https://docs.python.org/3/library/struct.html
packer = struct.Struct('I d d d d') #I=unsigned int, i=int, d=double
ackPacker = struct.Struct('I')

# Create a TCP/IP socket
sock = socket.socket(socket.AF_INET, socket.SOCK_STREAM)

HOST='127.0.0.1'
PORT = 65124

# # Bind the socket to the port
# server_address = (HOST, PORT)
# print('starting up on %s port %s' % server_address)
# sock.bind(server_address)

# #Calling listen() puts the socket into server mode, and accept() waits for an incoming connection.
# # Listen for incoming connections
# sock.listen(1)


with socket.socket(socket.AF_INET, socket.SOCK_STREAM) as s:
    s.bind((HOST, PORT))
    s.listen()
    conn, addr = s.accept()
    with conn:
        print('Connected by', addr)
        while True:
            # data = conn.recv(1024) #data size in bytes
            data = conn.recv(packer.size) #data size in bytes

            if not data:
                break #usually does not happen!

            unpacked_data = packer.unpack(data)
            print('data=',unpacked_data, ', len=',len(unpacked_data))

            chksum = sum(data) #checksum of packed bytes
            ackData = ackPacker.pack(int(chksum+unpacked_data[1]))
            conn.sendall(ackData)



# while True:
#     # Wait for a connection
#     print('waiting for a connection')
#     connection, client_address = sock.accept()
# #accept() returns an open connection between the server and client, along with the address of the client. The connection is actually a different socket on another port (assigned by the kernel). Data is read from the connection with recv() and transmitted with sendall().

# try:
#     print('connection from', client_address)

#     # Receive the data in small chunks and retransmit it
#     while True:
#         data = connection.recv(16)
#         print('received "%s"' % data)
#         if data:
#             print(sys.stderr, 'sending data back to the client')
#             connection.sendall(data)
#         else:
#             print('no more data from', client_address)
#             break

# finally:
#     # Clean up the connection
#     connection.close()