In case the previously posted guide wasn't working for you...

1. Router Setup
a. Open command prompt and enter the command 'ipconfig'
b. Note your ipv4 address and your default gateway
i. Default gateway will be your router
c. Log into your router by entering the IP address into google chrome
i. This assumes you know the credentials to log in
ii. Could be admin/admin or admin/password if nobody has set it up
d. Enable port forwarding
i. This is probably in advanced settings
e. Add entry to forward port 6883 for tcp/udp to your IPv4 address
i. Name the service "Bloody Trapland"
ii. If it asks for server IP address that will be your IPv4 address

2. Windows Firewall Setup
a. On host computer go to start menu search bar and type "windows firewall with advanced security"
i. Open it
b. Create 3 firewall rules for both inbound list and outbound list (so 6 total)
i. Right click the inbound or outbound list tab and hit 'New Rule…'
ii. Choose port and enter 6883 for TCP and name the entry "Bloody Trapland"
iii. Choose port and enter 6883 for UDP and name the entry "Bloody Trapland"
iv. Choose program, click next and browse to "Bloody Trapland.exe"
Likely in C:\Program Files (x86)\Steam\SteamApps\common\Bloody Trapland
(Name the entry "Bloody Trapland")
***Remember, be sure to complete steps ii, iii, and iv for both inbound and outbound lists.

That should be all that is necessary to host games for Bloody Trapland. I disable the firewall rules when not playing and re-enable them when I want to host a game.