Host Private Server

As to not ruin your own experience and invade public servers, you can host your own with little effort, so you and your friends can play by your own rules and your own pace. Rest of this guide is going to refer to Host as the person hosting the server and Client as any players joining the server of the host.

All players must have all content that the group wants to play: maps, mods, your own modifications, etc. and the only independent thing is skins, which don't cause a mismatch when joining the server.

Online Method

This is likely the most complicated method for the host and simplest for the client. Providing the best ping/most stable connection compared to any VLAN options.

If the host has the multiplayer patch installed, the hosted server will pop up for any clients and the public, who have that patch installed. If you do not wish to leak your IP, you might want to avoid installing the patch, as in the server browser any clients can simply join by clicking DIRECT IP and entering the IP. If it's listed with the server patch, a password will be neccessary to avoid random people.

Host

You must open the 10480 port in your router, as you likely have one. For this, you must Google something along the lines of "Portforwarding for 'insert model/manufacturer of router' " and follow the instructions, as all routers are wildly different. After that, you'll need to add exceptions to your firewall for that port. Again, different operating systems/antivirus software/etc. can make this step wildly different for everyone. After those two steps are complete, simply click Host Game in the main menu. In the Host game screen, make sure to set it to Internet. Set a password if you have the multiplayer patch, all other settings are pretty irrelevant and up to you, maps can always be voted to anything you want once in the game.

Client

If the multiplayer patch is present, navigate to Join Game and find the server. If not or you're unable to find it, in the Internet tab, click DIRECT IP and fill in relevant info.

VLAN - GameRanger

From my experience, GameRanger provides the most stable connection out of all VLAN (Virtual Local Area Network) methods, but is the most convoluted way to play.

Host and Client

1. Download and install GameRanger following steps on-screen until you get to the main window.
2. SWAT 4 and SWAT 4 The Stetchkov Syndicate have thier respective entires, but still might need linking the .exe files. If you're playing overhaul mods like SEF, you'll need to navigate to the Extras folder where the executable for the game is and rename it to Swat4X.exe. Renaming and linking the .exe will have to be done every time you switch/update mods.
3. In the main window of GameRanger, top menu bar click Edit and then Options.
4. In the Gamestab, select any game by clicking on it once and start typing swat, it should jump you down to the relevant entry.
5. Highlight SWAT 4: The Stetchkov Syndicate and click Browse..., then navigate to where you renamed the executable to Swat4X.exe and select it. Confirm your changes to get back to the main window.

Host

1. In the main GameRanger window, towards the top-right, press Hostand set the options to your room, add a password.
2. Bottom-right of your new window with the room, you will need to click the button Start, which will launch the game for you.
3. Once in-game, simply click Host Game. Make sure to set the server to host on LAN. Password not neccessary since your room has one. Most settings are irrelevant and maps can be voted back-to-back manually, so no need to pick the rotation out of the list.

Client

1. In the main GameRanger window, middle of the screen, you should see a dropdown menu, there you can select to sort by My Games and you will see SWAT 4: The Stetchkov Syndicate rooms. Join the room of your host.
2. Bottom-right of your new window with the room, you will need to click the button Join, which will launch the game for you.
3. Once the host has started the server, simply click Join Game and in your LAN tab, you should see the server.

VLAN - Radmin, etc.

There are plenty of VLAN software, with most of it simpler to use than GameRanger, but your experience may vary.

You can use Radmin to achieve hosting a server. Once downloaded and installed, in the Network menu, the host clicks Create a Network and clients click Join a Network... and enter relevant information. After that, it's a matter of the Host clicking Host Game in the main menu. Make sure to set the server to host on LAN; other settings once again are up to own choice; password not needed; maps can be voted without putting them in rotation. Clients clicking Join Game will find the server in the LAN tab.

Hamachi has the same exact steps, but requires registration after installation and is limited to 5 people per Network. Though has the advantage of being cross-platform.

There are plenty of other choices you can use. It's a matter of Googling them and picking your poison. Most are just as easy to set up as Radmin and Hamachi.