深入理解C语言网络编程中的send函数

#include <stdio.h> #include <stdlib.h> #include <unistd.h> #include <string.h> #include <netinet/in.h> #include <arpa/inet.h> #include <sys/socket.h> #include <sys/types.h> #include <errno.h> typedef struct data { char name[30]; unsigned int num; }Data; void print_err(char *str, int line, int err_no) { printf("%d, %s :%s\n",line,str,strerror(err_no)); _exit(-1); } int main() { int skfd = -1, ret = -1; skfd = socket(AF_INET, SOCK_STREAM, 0); if ( -1 == skfd) { print_err("socket failed",__LINE__,errno); } struct sockaddr_in addr; addr.sin_family = AF_INET; //设置tcp协议族 addr.sin_port = 6789; //设置端口号 addr.sin_addr.s_addr = inet_addr("192.168.102.169"); //设置ip地址 ret = bind(skfd, (struct sockaddr*)&addr, sizeof(addr)); if ( -1 == ret) { print_err("bind failed",__LINE__,errno); } /*将套接字文件描述符从主动转为被动文件描述符，然后用于被动监听客户端的连接*/ ret = listen(skfd, 3); if ( -1 == ret ) { print_err("listen failed", __LINE__, errno); } /*被动监听客户端发起的tcp连接请求，三次握手后连接建立成功*/ int cfd = -1; struct sockaddr_in caddr = {0};//为应用层获取客户端的IP和端口号 int csize = 0; cfd = accept(skfd, (struct sockaddr*)&caddr, &csize); if (-1 == cfd) { print_err("accept failed", __LINE__, errno); } printf("cport = %d, caddr = %s\n", ntohs(caddr.sin_port),inet_ntoa(caddr.sin_addr)); //发送数据结构体定义 Data std_data = {0}; while (1) { printf("stu name:\n"); scanf("%s",std_data.name); //对于int型的需要将主机端序转换为网络端序，这里转成long型。 printf("stu num:\n"); scanf("%d",&std_data.num); std_data.num = htonl(std_data.num); //将数据std_data强制类型转换后发送 ret = send(cfd, (void *)&std_data,sizeof(std_data),0); if ( -1 == ret) { print_err("accept failed", __LINE__, errno); } } return 0; }