client.println("[STX]MVR=1[ETX]"); //send signal to initialize motor
client.println("[STX]SPD="); //send signal to set speed
client.println(PotVal/10.23); //Can't figure out how to set the pot value in the middle of the ascii values i.e. [STX]SPD=PotVal/10.23[ETX]"
client.println("[ETX]");
Are you sure that you are supposed to be sending the string "[STX]", not the VALUE STX?