Firewalls and hosting games

Support
If players are not able to join your game, you may have a firewall in place. Firewalls may prevent incoming networks from reaching your computer and prevent you from hosting games.

A firewall can come in many forms. In households, they may exist as security software, router and/or modem. The following information will help you configure your firewall.

Ports

Ports can be thought of as points of connection. The game listens to these ports to receive all of the information it needs to function. You will need the following ports opened to allow your game to accept connections and to host games:

Diablo and Warcraft II Battle.net Edition:
Allow port 6112-6119 TCP and UDP out and in

Diablo II:
Allow port 6112 TCP out and allow established sessions in
Allow port 4000 TCP out (realm games)
Allow port 4000 TCP out and in (hosting open games only)

StarCraft:
Allow port 6112 TCP and UDP out and in

Warcraft III:
Allow port 6112 TCP out and allow established sessions in
Allow port 6112 TCP in (hosting custom games)
Allow port 6113-6119 TCP out and in (hosting custom games if you have changed the default port in the Options/Gameplay screen)

World of Warcraft:
Allow port 3724 TCP out and in for Game
Allow port 3724 UDP out and in for Voice Chat

Blizzard Downloader:
Allow port 6881-6999 TCP and UDP out and in
Allow port 3724 TCP out and in
Allow port 6112 TCP out and in

For detailed information about ports and their functions, please visit our support site information on Ports.

Software Firewalls

You may recognize names such as Norton Internet Security, McAfee Personal Firewall Plus/Express, ZoneAlarm, Sygate, Panda, and many others. These security programs act as firewalls that can block single programs or specific ports from the network.

More information on these can be found here

Hardware Firewalls

Virtually all routers available today have firewall functions to protect users from outside access. In addition to this, DSL and Cable modems may have firewall functions as well. These links will give you information on how to configure your products. For port numbers and information, please see above.

Almost-everything Port Forwarding Related
List of default usernames and passwords for routers
Belkin Networking Support:
D-Link Port Forwarding
Linksys Port Forwarding
Netgear Port Forwarding
USRobotics Support
ZyXEL Support

Notes and exceptions
There are a few things to make note of.
Warcraft III is the only Blizzard Title that currently supports multiple players hosting games behind NAT. Other games are not able to do this.

You may experience high latency with StarCraft, Warcraft II, and Diablo when joining the same game from the same connection. These games were not designed to use a shared connection.
If you have recently patched a game and get "Unable to connect", a software firewall may be blocking the game change. Please configure it to allow the changed game.

A "universal rule" for a hardware firewall may work for all Blizzard Battle.net games. Forward ports 4000 TCP and 6112-6119 TCP/UDP to your computer. For the Blizzard Downloader, if you have bittorrent set up already just allow port 6112 TCP and 3724 TCP.

Port Triggering may work better for you depending on your router. Note that port triggering may fail if there is a second computer playing on the same game/port.

Common issues

If you did not change your networking equipment and you suddenly are not able to host, your internal IP address may have changed. Check your router's Port Forward section and make sure it is still forwarding information to the right computer.

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