c - What can be the reasons of connection refused errors?

Question

I'm trying to write a server program in C, using another client, I get this error when I try to connect through port 2080 for example.

connection refused

What can be the reasons of this error?

Answer 1

There could be many reasons, but the most common are:

1. The port is not open on the destination machine.

2. The port is open on the destination machine, but its backlog of pending connections is full.

3. A firewall between the client and server is blocking access (also check local firewalls).

After checking for firewalls and that the port is open, use telnet to connect to the ip/port to test connectivity. This removes any potential issues from your application.