How to send data from C# to python using sockets?

Question

I cannot find any example or a tutorial on how to send data from C# to python.

in my application, C# is supposed to keep reading data from a hardware and send it to python to be processed. i have tried to create a basic server on python and a basic client on C# and i was never able to establish connection between the client and the server with the following output from C# No connection could be made because the target machine actively refused it. i tested my python server on a python client and i was able to establish connection just fine.

how do i send data from C# to python correctly using sockets? is there any available tutorial on example i can follow? is there something wrong with my code? here it is:

Python Server code:

import socket

s = socket.socket(socket.AF_INET, socket.SOCK_STREAM)
s.bind((socket.gethostname(), 1234))
s.listen(5)

while True:
    clientsocket, address = s.accept()
    print(f"Connection from {address} has been established!")
    clientsocket.send(bytes("Welcome to the server!", "utf-8"))
    clientsocket.close()

C# Client Code:

 static void ExecuteClient()
        {

            try
            {

                IPHostEntry ipHost = Dns.GetHostEntry(Dns.GetHostName());
                IPAddress ipAddr = ipHost.AddressList[0];
                IPEndPoint localEndPoint = new IPEndPoint(ipAddr, 1234);

                Socket sender = new Socket(ipAddr.AddressFamily,
                           SocketType.Stream, ProtocolType.Tcp);

                try
                {
                    sender.Connect(localEndPoint);

                    Console.WriteLine("Socket connected to -> {0} ",
                                  sender.RemoteEndPoint.ToString());

                    byte[] messageReceived = new byte[1024];

                    int byteRecv = sender.Receive(messageReceived);
                    Console.WriteLine("Message from Server -> {0}",
                          Encoding.ASCII.GetString(messageReceived, 0, byteRecv));

                    sender.Shutdown(SocketShutdown.Both);
                    sender.Close();
                }

                // Manage of Socket's Exceptions 
                catch (ArgumentNullException ane)
                {

                    Console.WriteLine("ArgumentNullException : {0}", ane.ToString());
                }

                catch (SocketException se)
                {

                    Console.WriteLine("SocketException : {0}", se.ToString());
                }

                catch (Exception e)
                {
                    Console.WriteLine("Unexpected exception : {0}", e.ToString());
                }
            }

            catch (Exception e)
            {

                Console.WriteLine(e.ToString());
            }
        }

Answer 1

I know this question is old, but incase some else stumbles here in their internet searching.

I just started down the road of learning Python and I'm working on a similar situation with my Raspberry Pi (SERVER) and Windows PC (CLIENT).

The problem is you're making a call to get the hostname on each machine. This is will obviously be different. Your client needs to connect to the address of the server. Your client code is trying to connect to the machine it's running and that connection is being refused. The server is never contacted.

I made the following changes and was able to establish a connection.

Python Server code:

s.bind(("", 1234))

C# Client Code:

//IPHostEntry ipHost = Dns.GetHostEntry(Dns.GetHostName());
//IPAddress ipAddr = ipHost.AddressList[0];
IPEndPoint localEndPoint = new IPEndPoint(IPAddress.Parse("[SERVER IP]"), 1234);

Server Console Response:

Connection from ('[CLIENT IP]', 52074) has been established!   

Client Console Response:

Socket connected to -> [::ffff:[SERVER IP]]:1234 
Message from Server -> Welcome to the server!