common_setup
int port = common_setup(context, &argc, argv, server_usage);
int port = common_setup(context, &optind, argv, client_usage);
int port = common_setup(context, &argc, argv, usage);
s = common_setup(SOCK_SEQPACKET, "/var/run/devd.seqpacket.pipe");
s = common_setup(SOCK_STREAM, "/var/run/devd.pipe");