Engine Error: Couldn't allocate any server IP port

[prisencolinensin]

Hello,
I'm trying to run a garry's mod dedicated server off of my computer. I've port forwarded ports 27000-27050, just for good measure.
This is the script I'm using to start up the server:
@echo off
cls
echo Protecting srcds from crashes...
title srcds.com Watchdog
:srcds
echo (%time%) srcds started.
start /wait srcds.exe -console -game garrysmod +login anonymous -port 27015 +ip <my_ip> +map rp_downtown_evilmelon_v1 +gamemode darkrp +maxplayers 16
I've also went into my advanced firewall settings on my computer and created inbound and outbound exceptions for both srcds.exe and ports 27000-27050.
I'm fairly certain I'm port forwarding correctly, because I'm doing it the same way that I did it a year ago, and back then it worked just fine.
I've tried using tools like Open Port Check Tool, and none of my ports were open. Then I tried going through the command prompt and typing netstat -ab to check if any of the programs on my computer were taking up those ports. Nothing on my computer is taking up these ports.
I tried turning off my firewall, and I still got the same error. I figure that the only possible reason why this isn't working is because of something with my ISP, but again, this was working about a year ago, is it possible that they've changed something? And if they have changed something, does that mean I'm shit out of luck? Is there anything else I could try?

[lubatron]

do you use steamcmd

[prisencolinensin]

I port forwarded that port, and tried -port 27015 in my start.bat, and it didn't work.

[Rubat]

Most likely you are trying to force it to allocate the ports of wrong IP you gave it.

[prisencolinensin]

Am I supposed to use my internal or external IP in the start.bat? Right now I have it set to try to run on my external ip address, and I'm confident that I'm using the right external IP address.