The error "System call error: Address already in use tcp server bind - exiting" is indicative of a hung port (see Solution # 151). One needs to kill Shareplex processes if any, clean up the shared memory/semaphores and then relaunch Shareplex. The error can also happen if someone tries to start sp_cop while another one is still running. You can check by issuing "ps -ef|grep sp_" at Unix OS level.
So if there was no hung port and if the sp_cop failed to start when one was already running, all you have to do is to launch sp_ctrl to work with Shareplex since you do not need to start the Shareplex instance when it is already running.