rem: OpnSession *session = (OpnSession *) udata;
context: OPN_HANDLER(ping){	OpnSession *session = (OpnSession *) udata;	OpnPacket *pong;	assert(session);	if (!(pong = opn_packet_new()))		return;	opn_packet_set_cmd(pong, OPN_CMD_PONG);	opn_packet_put_str(pong, packet->read, FALSE);	opn_packet_send(pong, session->con);	opn_packet_free(pong);}