Let's imagine you do not have a working internet connection, or you do not have a player to test your map every time you need to.
1. First copy and paste your entire directory of Sudden Strike Forever somewhere else on your choosen hard drive partition, so now you have two Sudden Strike Forever games.
2. Copy and paste your multiplayer map .smm file from the first game in Maps - mplay folder in the other game directory.
3. Make two shorcuts of the two games on the desktop or in the taskbar.
4. Start the first shorcut, go to ,,Multiplayer - Internet (Tcp/Ip), give yourself a ,,Player name,, above and click ,,Create game,,. Find your map and click ,,Ok,,.
Choose your nation, team number above the screen and click ,,Ready,,.
5. Click the ,,Window,, on your keyboard or just Ctrl+Esc to minimize the game to desktop tray bar.
6. Start the second shorcut, go to ,,Multiplayer - Internet (Tcp/Ip), give yourself a ,,Player name,, above and click ,,Join game,, and click ,,Ok,,. You now see your own made server, so click ,,Join game,, again. Choose your nation, a different team number above the screen and click ,,Ready,,.
Again, minimize your game to desktop tray.
7. This last step is important so you do not crash your games:
Click the first shorcut from the desktop tray to maximize the first game window (the first game that made the server). Click ,,Start,, and then quickly minimize to tray.
Click the second game shorcut on the tray, and here you go. :)
Test your map and you can switch between windows every time you want.