#include <stdio.h> #include <unistd.h> #include <netdb.h> int main(int argc,char *argv[]) {   struct servent serv;   struct servent *serv_info=&serv;   serv_info=getservbyport(htons(atoi(argv[1])),NULL);/*第二个参数为协议类型，为NULL时自动匹配所有协议*/   printf("%s\n%d\n",serv_info->s_name,ntohs(serv_info->s_port));   serv_info=getservbyport(htons(atoi(argv[1])),"tcp");                 printf("%s\n%d\n",serv_info->s_name,ntohs(serv_info->s_port));      return 0; }