If you love playing Half-Life and co-op as much as I do then this is the free piece of software to bond them together! Half-Life 2 is great playing with friends. Synergy enables Half-Life 2 to be played co-op. Here is what I did to get it working.

Enjoy!!

Playing Half-Life 2 co-op using Synergy
Both game host and client:
Download and install Half-Life 2:
http://steamproxy.net/steamstore/app/220/?snr=1_7_15__13

Download and install Synergy (free):
http://steamproxy.net/steamstore/app/17520/?snr=1_7_15__13

Game host:
1) Open port 27015 TCP and UDP on your router
2) Get your REAL internet IP address (shown at the bottom left hand corner) and give this number to the client joining your game:
http://www.speedtest.net/
3) Start up Synergy
4) Start server for Half-Life 2 from the Synergy menu options

Note: Them trying to join your game via Steam friends or sending them game invites will NOT work. It will try connecting to the actual IP address of your PC (usually 192.168.x.x) which is local and not public. You will get host connect failures.

Client:
1) Start Synergy
2) Enable Developer Console:
The console starts disabled by default. To enable it, load the game and visit Options > Keyboard > Advanced. There will be a pop-up that will include two options, one of them labeled "Enable Developer Console". Once enabled, it can be opened and closed by pressing the button above Tab ⇆, known as the "tilde." ~

3) Enter Developer Console with the ~ key and enter connect command to the host internet IP address:
~
connect xx.xx.xx.xx

You then should be connected and able to play co-op!

If you love playing Half-Life and co-op as much as I do then this is the free piece of software to bond them together! Half-Life 2 is great playing with friends. Synergy enables Half-Life 2 to be played co-op. Here is what I did to get it working. Enjoy!! Playing Half-Life 2 co-op using Synergy Both game host and client: Download and install Half-Life 2: http://steamproxy.net/steamstore/app/220/?snr=1_7_15__13 Download and install Synergy (free): http://steamproxy.net/steamstore/app/17520/?snr=1_7_15__13 Game host: 1) Open port 27015 TCP and UDP on your router 2) Get your REAL internet IP address (shown at the bottom left hand corner) and give this number to the client joining your game: http://www.speedtest.net/ 3) Start up Synergy 4) Start server for Half-Life 2 from the Synergy menu options Note: Them trying to join your game via Steam friends or sending them game invites will NOT work. It will try connecting to the actual IP address of your PC (usually 192.168.x.x) which is local and not public. You will get host connect failures. Client: 1) Start Synergy 2) Enable Developer Console: The console starts disabled by default. To enable it, load the game and visit Options > Keyboard > Advanced. There will be a pop-up that will include two options, one of them labeled "Enable Developer Console". Once enabled, it can be opened and closed by pressing the button above Tab ⇆, known as the "tilde." ~ 3) Enter Developer Console with the ~ key and enter connect command to the host internet IP address: ~ connect xx.xx.xx.xx You then should be connected and able to play co-op!