How to connect client/server in C (Beej's Guide to Network Programming)

Question

I am working through a simple tutorial for C network programming found here: https://beej.us/guide/bgnet/html/multi/index.html

After reading through it, my plan was to implement a testing client/server program, and then start to play around, modify things, add stuff, etc. I implemented the program found here (the first client/server set dealing with TCP connections): https://beej.us/guide/bgnet/html/multi/clientserver.html

Basically, a "server" runs on one machine, and when the client connects, the server just sends "Hello, world!" This works fine when I run both on the same machine and connect to localhost.

However, I am unable to connect between different machines (tried on both a Debian and OpenBSD server, no iptables/pf rulesets). The connection just times out, and I'm not really sure why. I can ping and ssh into both.

Can anyone, specifically anyone familiar with this tutorial, point me in the right direction?

Edit: no X on servers, so no screenshots, but netstat -tlnp | grep 3490 gives me nothing.

netstat -an shows tcp connection listening on 3490.

Answer 1

I don't see your servinfo being filled any where in the code

// Server should allow connections from any ip address

  serv_info.sin_addr.s_addr = INADDR_ANY;

Also you might need to fill family and port

// Fill server's address family

  serv_addr.sin_family = AF_INET;

To need more details, here is a working server i wrote on a forum http://forum.codecall.net/topic/63924-a-simple-tcp-server-using-linux-c-api/

Answer 2

Right before if (bind(sockfd, p->ai_addr, p->ai_addrlen) == -1) { print out the value of p->ai_addr I'd bet it's 127.0.0.1. This would cause communication to work fine on one computer, but not happen anywhere else.

To listen on all interfaces, bind on 0.0.0.0.