close down all processes using a certain port
close <port> (<signal (default SIGKILL)>)-1-SIGHUP-2-SIGINT-3-SIGQUIT-4-SIGILL-5-SIGTRAP-6-SIGABRT-7-SIGBUS-8-SIGFPE-9-SIGKILL-10-SIGUSR1-11-SIGSEGV-12-SIGUSR2-13-SIGPIPE-15-SIGTERM-17-SIGCHLD-19-SIGSTOP