socket接口
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
int socket(int domain, int type, int protocol);
返回：成功返回描述符，失败返回-1
绑定地址，成功返回0，出错返回-1
int bind(int sockfd, const struct sockaddr *addr,
socklen_t addrlen);
================================
struct sockaddr_in {
short int sin_family;
unsigned short int sin_port;
struct in_addr sin_addr;
unsigned char sin_zero[8];
}
struct in_addr {
unsigned long s_addr;
}
================================
查找绑定到套接字的地址，成功返回0，出错返回-1
int getsockname(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
获取对方地址，成功返回0，出错返回-1
int getpeername(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
服务器端：
backlog 指定进行客户端连接排队的队列长度
int listen(int sockfd, int backlog);
int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen);
客户端：
int connect(int sockfd, const struct sockaddr *addr,socklen_t addrlen);
TCP/IP编程模型
image.png
基于TCP协议的服务器端
等待客户端连接，返回当前服务器时间给客户端。
#include <arpa/inet.h>
#include <netdb.h>
#include<sys/socket.h>
#include<unistd.h>
#include<string.h>
#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
#include<signal.h>
#include<time.h>
int sockfd;
void sig_handler(int signo) {
if (signo == SIGINT){
printf("server close\n");
/*步骤6：关闭服务器端的socket*/
close(sockfd);
exit(1);
}
}
void out_addr(struct sockaddr_in *clientaddr) {
//将端口从网络字节序转换成主机字节序
int port = ntohs(clientaddr->sin_port);
char ip[16];
memset(ip, 0, sizeof(ip));
//将ip地址从网络字节序转换成点分十进制
inet_ntop(AF_INET, &clientaddr->sin_addr.s_addr, ip, sizeof(ip));
printf("client:%s(%d) connected\n", ip, port);
}
void do_service(int fd) {
// 获得系统时间
long t = time(NULL);
char *s = ctime(&t);
size_t size = strlen(s) * sizeof(char);
if (write(fd, s, size) != size) {
perror("write error");
}
}
int main(int argc, char *argv[]) {
if (argc < 2){
printf("usage:%s #port\n",argv[0]);
exit(1);
}
if (signal(SIGINT, sig_handler) == SIG_ERR){
perror("signale sigint error");
exit(1);
}
/*步骤1：创建socket套接字*/
sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0){
perror("socket error");
exit(1);
}
/*步骤2：调用bind将socket和地址绑定(包括ip，port)*/
struct sockaddr_in serveraddr;
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sin_family = AF_INET; //IPV4
serveraddr.sin_port = htons(atoi(argv[1]));
serveraddr.sin_addr.s_addr = INADDR_ANY;
if(bind(sockfd, (struct sockaddr *)&serveraddr,sizeof(serveraddr)) < 0) {
perror("bind error");
exit(1);
}
/*步骤3：调用listen函数启动监听(指定port监听)*/
if(listen(sockfd,10) < 0) {
perror("listen error");
exit(1);
}
/*步骤4：调用accept函数从队列中获得一个客户端的请求连接
注意：若没有客户端连接，调用accept函数将阻塞，直到货到衣蛾客户端连接
*/
struct sockaddr_in clientaddr;
socklen_t clientaddr_len = sizeof(clientaddr);
while (1){
int fd = accept(sockfd,
(struct sockaddr *)&clientaddr,
&clientaddr_len);
if(fd < 0) {
perror("accept error");
continue;
}
/**
* 步骤5：调用IO函数(read/write)和连接的客户端进行双向的通信
*/
out_addr(&clientaddr);
do_service(fd);
/*步骤6：关闭客户端的socket*/
close(fd);
}
return 0;
}
启动服务器端，监听8888端口
image.png
使用nc命令连接服务器端：
1669857335301.png
##基于TCP协议的客户端
#include <arpa/inet.h>
#include <netdb.h>
#include<sys/socket.h>
#include<unistd.h>
#include<string.h>
#include<stdio.h>
#include<stdlib.h>
#include<memory.h>
#include<signal.h>
#include<time.h>
int main(int argc, char *argv[]) {
if (argc < 3){
printf("usage:%s ip port\n",argv[0]);
exit(1);
}
/*步骤1：创建socket*/
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
if (sockfd < 0){
perror("socket error");
exit(1);
}
// 往serveraddr里填入ip，port和地址族类型(ipv4)
struct sockaddr_in serveraddr;
memset(&serveraddr, 0, sizeof(serveraddr));
serveraddr.sin_family = AF_INET;
serveraddr.sin_port = htons(atoi(argv[2]));
inet_pton(AF_INET, argv[1], &serveraddr.sin_addr.s_addr);
/*步骤2：客户端调用connect函数链接到服务器端*/
if(connect(sockfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) < 0) {
perror("connect error");
exit(1);
}
/*步骤3：调用IO寒素(read/write)和服务器端双向通信*/
char buffer[1024];
memset(buffer, 0 ,sizeof(buffer));
size_t size;
if ((size = read(sockfd, buffer, sizeof(buffer))) < 0){
perror("read error");
}
if (write(STDOUT_FILENO, buffer, size) != size){
perror("write error");
}
/*步骤4：关闭socket*/
close(sockfd);
return 0;
}
网友评论