检测服务器端口是否被占用

for (int port=begin; port <= end; port++){
        /*定义socket*/
        int server_sockfd = socket(AF_INET, SOCK_STREAM, 0);

        /*定义sockaddr_in 的变量*/
        struct sockaddr_in server_sockaddr;
        server_sockaddr.sin_family = AF_INET;
        server_sockaddr.sin_addr.s_addr=htonl(INADDR_ANY);
        server_sockaddr.sin_port = htons(port);
        //server_sockaddr.sin_port = 0; /*端口范围是0～65535 1~1023为保留端口号*/
       
        /*检查端口占用情况，列出占用端口号*/
        if (bind (server_sockfd, (struct sockaddr *) &server_sockaddr, sizeof(
        server_sockaddr)) == -1){
            printf ("%d
", port);
            alread_port_cnt++;
            //break;
        } else {
            idle_port_cnt++;
        }
        close (server_sockfd);
    }/*循环结束*/

用bind()函数就可以，成功返回0, 占用返回-1.