Foreword: Before reading further, note that you cannot host on battle.net if you use public Wi-Fi or an unconfigurable modem. These instructions assume that you can add ports to your router.

Problem: People can't join your game on battle.net because of your router's firewall

Error:
StarCraft Battle.net Host/Join Error

You were unable to join. The game you have selected is not responding. The latency to the game creator is too high.

Solution: On your main computer, log into your router's intranet page and set its firewall to open ports 6112 to 6119 TCP.

Step 1:  Start button -> Run/Search -> type "cmd" -> Command Prompt is opened, type "ipconfig".
If you are using Mac OS, open the Terminal and type "ifconfig".

C:\Documents and Settings\Admin>ipconfig

Windows IP Configuration


Ethernet adapter Local Area Connection:

        Connection-specific DNS Suffix  . : gateway.2wire.net
        IP Address. . . . . . . . . . . . : 192.168.1.65
        Subnet Mask . . . . . . . . . . . : 255.255.255.0
        Default Gateway . . . . . . . . . : 192.168.1.254

C:\Documents and Settings\Admin>_

Step 2: Your router's webpage address should be the Default Gateway, type those numbers into your browser's address bar, for example: http://192.168.1.254 If the address is correct, you may see a login prompt, try these following name/password combinations: admin/admin, admin/(blank), (blank)/(blank), admin/password, admin/1234, admin/123 If the router's webpage does not load or you can't access it, physically pick up your router and look for its model number, then go to this routers list and choose your model. That site's instructions will tell you the proper address, login, and password.

Step 3: After logging in to your router, look for a section that may be called Port Forwarding, or Port Triggering, or Firewall Settings, or NAT Configuration, or Virtual Server, or Security--which are usually located in an Advanced Settings category. This page will usually have a list of 192.168.1.XXX addresses and input boxes for a specific computer, program, protocol, or port number. Your goal is to find a page that looks something like the one below:

Router port forwarding for StarCraft Battle.net

Step 4: If the page asks for the computer to forward to, select your computer's name if it is there; if it asks for the IP number, use the "IP Address" you previously got from the command prompt. After that, add ports 6112 to 6119 for TCP and then UDP, or just 6112 if your router does not allow port ranges. Click the Save/Submit button in the configuration page and your router will automatically reset.

Conclusion: If there no other conflicts or problems with your network, you now should be able to host games on battle.net. Otherwise, check your firewall program and allow StarCraft.exe in its filters. Read this battle.net thread for more technical resources.

Note: This does not solve the "blank screen" problem on the game list as it is inherent with battle.net

Resources: LAN Configuration Tutorial
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