port-forward

Global Socket Port Forwarding

Connect to a firewalled host

Problem
A hypothetical example for BOB to connect to ALICE's IRCD. Both are on two different networks and behind a NAT/Firewall. Neither of them can reach the other.

Objective
Allow BOB to access ALICE's (private) IRCD service (without tampering with the firewall, NAT or router settings).

Solution
Create a port forward to ALICE's IRCD and make this forward accessible via the Global Socket Relay network (GSRN).

Prerequisite IRCD running on ALICE's workstation and an IRC client (irssi) on BOB's workstation.

On workstation "ALICE" create /etc/system/systemd/gs-portforward.service to configure a port forward from the Global Socket ExampleSecretChangeMe to TCP port 6667 on your workstation (127.0.0.1):

[Unit]
Description=Global Socket IRCD Forward
After=network.target

[Service]
Type=simple
Restart=always
RestartSec=10
ExecStart=gs-netcat -s ExampleSecretChangeMe -l -d 127.0.0.1 -p 6667

[Install]
WantedBy=multi-user.target

Start, check and enable the service:

root@ALICE:~# systemctl start gs-portforward
root@ALICE:~# systemctl status gs-portforward
root@ALICE:~# systemctl enable gs-portforward

On BOB's workstation create a port forward from TCP port 6667 to the Global Socket ExampleSecretChangeMe:

b@BOB:~$ gs-netcat -s ExampleSecretChangeMe -p 6667

TCP port 6667 on BOB's workstation is now forwarded to TCP port 6667 on ALICE's workstation. Bob connects to ALICE's IRCD as if the IRCD is running on his workstation (127.0.0.1):

b@BOB:~$ irssi -c 127.0.0.1

Alternatively of using two separate commands BOB can use the gsocket tool to start the irc client and automatically forward the connection via the GSRN:

b@BOB:~$ gsocket irssi -c blah.gsocket
Enter Secret (or press Enter to generate): ExampleSecretChangeMe
=Secret         :"ExampleSecretChangeMe"
=Encryption     : SRP-AES-256-CBC-SHA-End2End (Prime: 4096 bits)
Irssi v1.2.0-2 - https://irssi.org
06:22 -!- Irssi: Looking up blahgsocket
06:22 -!- Irssi: Connecting to blah.gsocket [127.31.33.7] port 6667
[...]

This is a hypothetical example. Alice can configure the port forward by changing 127.0.0.1 to the desired destination.

Alice created a port forward and started the IRCD service. Instead Alice can combine this into a single command:

alice@ALICE:~$ gsocket inspircd --nolog --nofork 
Enter Secret (or press Enter to generate): ExampleSecretChangeMe
=Secret         :"ExampleSecretChangeMe"
=Encryption     : SRP-AES-256-CBC-SHA-End2End (Prime: 4096 bits)
Inspire Internet Relay Chat Server
(C) InspIRCd Development Team.
[...]

Many more gs-netcat options are available: For example -T to connect via TOR or -L for log-output. See the manual page for gs-netcat.