tcp-server-client | 即时通信 select/poll/epoll | Socket library

I'm working on embedded system with modem and I want to connect from modem to anything that can show data from client and optionally send some data to client.

I'm looking for a tool that would:

• open TCP socket
• print some info when client connects
• print incoming data
• send some data to client, maybe input from console? (optional)
• print some info when client disconnects

I could just take this (or another socket example) and compile it:

https://www.geeksforgeeks.org/tcp-server-client-implementation-in-c/

but maybe there is something like this or much better in Debian APT repositories?

I'm new to networks and I'm wondering why this TCP Server-Client implementation in C only works on one computer? (1)

I mean I have to open one terminal for the server program and another one for the client program. But why this doesn't work between computers? Starting the server program on one computer and the client program on another computer.

How we need to modify the code to work between computers? (2)

And what are great resources to start on the whole topic? (3)

Problem: I am trying to set-up TCP socket read() and write() from the same main function, however I am unsure how to correctly read from the socket.

Background info: I have communication working with separate executables, one for the Reading(Server) and the other for Writing(Client).

To do this I used this site for guidance. https://www.geeksforgeeks.org/tcp-server-client-implementation-in-c/

I understand from Remy Lebeau's comment on C socket read and write that the socket returned by accept() is used by the Server and the socket returned from socket() is used by the Client.

I have the writing to the socket working correctly.

I have read the TCP-Server-Client and try to run my example but I am getting the following error: