Cybersecurity

I need to open a port in linux to allow a connect() from another box to succeed. I have the linux box listening on port 3000 on INADDR_ANY, and a Windows box does a connect to the IP of the linux box on that same port. The Linux box refuses the connection. I think it's because all the ports are closed except for the well-known ones. I want to open just port 3000 but I can't figure out how to do it. I don't want to associate any service or executable with the connection.

Are you asking how to open a hole in the firewall? If so, what version of the kernel are you running?

Yes. I want to poke a hole in the firewall.
BTW, I don't think it's running any firewall daemon. At least I don't recall setting one up.
It's Kernel 2.4 (Redhat 7.2).
Thx.

What process is listening on your port 3000?

My app. is listening. I create the socket, do the bind, listen, select, then accept when the select passes to set up the connection. These are stream-type TCP sockets. The code works fine locally, if I have the client and server on the same Windows machine. I haven't compiled the client on the Linux box yet.

Redhat 7.2 sets up an iptables-based firewall for you automatically during installation. To open a tcp port use something like:

iptables -A INPUT -s <source-ip/wildcard> -p tcp -m tcp --dport <port-number> -j ACCEPT


See the official HOWTo from one of the iptables authors here: http://netfilter.samba.org/unreliabl...WTO/index.html

See also: the iptables man page.

RedHat also comes with a GUI firewall configuration tool I believe.

I ported and compiled my client so they both ran on the Linux box, and I got the same error from connect() "ECONNREFUSED." I've also added an entry to /etc/services for my app and protocol/port and added a rule using ipchains. I also tried using both 127.0.0.1 and my LAN addr of the box 192.168.0.2 with the same result.