You can write something that will match Robin's Serial Input Basics - updated
In a simple form, you can send <N,valN> (including <' and >`. N is the number of the servo to control and valN the value for that servo. The receiver could than follow example 5 in the above link.
You can also control multiple servos using e.g. <M,valM;N,valN> to send data for two servos. And if you know that you're always will be sending commands for all servos, N and M can be omitted and you only send the values separated by commas.