From SA-MP Wiki
The Remote Console is a command prompt where you can use RCON commands without having to be in game and on your server. Since 0.3b the Remote Console got removed from the Server Browser. From now on you will have to use another way to access Remote RCON as explained below.
1. Open a text editor.
2. Write in the following line: rcon.exe IP PORT RCON-PASS.(Replace IP/PORT/PASS with your server details)
3. Save the file as rcon.bat
4. Put the file into your GTA directory where rcon.exe is located.
5. Run rcon.bat
6. Enter the command you like.
Note: There is no need to type "/rcon" before the command in the server browser and the commands will not work if you do. For Example if you want to reset the server just type "gmx" and hit enter. That is all you need to do. Enjoy