An attempt was made to access a socket in a way forbidden by its access permissions.

Is a typical message when blocked by a firewall so make sure DC++ is allowed using the FAQ below

eMTee suggests this article as an answer to your question:
FAQ #103: “My DC++ is probably blocked by a firewall. How can I unblock?”.

I've already done everything on that page before posting this question, I can't figure out how to get it to work.

Since your OS is Windows 7, are you using the latest version of DC++?

This user is using Windows 7, maybe this link could help you: https://answers.launchpad.net/dcplusplus/+question/100379

I tried the test and got 3, 5 and 6 failed. I then tried to follow the instructions on how to fix 3, which promptly shut down my computer. What should I do now?

And I tried restarting DC++ but that won't work either.

In order for Number 3 & 5 to pass, click the Windows icon on the bottom of your left screen, on Start Search, type Service.msc & hit Enter on keyboard.

Scroll down & look for:
3. SSDP Discovery should be set to Automatic under Startup Type, hit the Apply button and close the Dialogue box by clicking OK.
5. UPnPHost Device Host should be set to Automatic under Startup Type, hit the Apply button and close the Dialogue box by clicking OK.

Go to Control Panel, Network/Sharing Center & turn On Network Discovery.

On the Home or Work (Private) Networks, Windows Firewall should be turned Off not On. Make sure your anti-virus is enabled so you are not vulnerable to hackers, malicious software, viruses & create an allow rule for DC++ since you are on Windows 7.

Let me know if you have all 6 of 8 passed when you test UPNPTest. If so, you have 7 & 8 failed then. You need port forwarding by going to http://www.portforward.com. On PortForward's page, look for the make & model of your router. Here's an example, 2Wire (Make) 2701 HG-B (Model). To find out your router, look for the make & model if your modem is near or next to your PC.

Active mode on Windows 7 has the same configuration as Vista.