一、问题引入
阅读UNIX网络编程 卷1：套接字联网API 第3版的前4个章节，觉得有必要对书籍上的源码案例进行复现，并推敲TCP的C/S通信过程。
二、解决过程
2-1 server
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/shm.h>
#define PORT 8887
#define QUEUE 20
#define BUFFER_SIZE 1024
int main()
{
// 定义sockfd, AF_INET:IPv4协议，SOCK_STREAM：字节流套接字
int server_sockfd = socket(AF_INET, SOCK_STREAM, 0);
// 定义sockaddr_in
struct sockaddr_in server_sockaddr;
server_sockaddr.sin_family = AF_INET;
server_sockaddr.sin_port = htons(PORT);
server_sockaddr.sin_addr.s_addr = htonl(INADDR_ANY);
// bind，成功返回0，出错返回-1
if (bind(server_sockfd, (struct sockaddr *)&server_sockaddr, sizeof(server_sockaddr)) == -1)
{
perror("bind failure");
exit(1);
}
// listen，成功返回0，出错返回-1
if (listen(server_sockfd, QUEUE) == -1)
{
perror("listen failure");
exit(1);
}
// 客户端套接字
char buffer[BUFFER_SIZE];
struct sockaddr_in client_addr;
socklen_t length = sizeof(client_addr);
// 成功返回非负描述字，出错返回-1
// accept()被阻塞，等待客户端连接，一旦客户端和服务器完成TCP三次握手，accept()返回一个已连接描述值
int conn = accept(server_sockfd, (struct sockaddr *)&client_addr, &length);
if (conn < 0)
{
perror("connect failure");
exit(1);
}
printf("**************************n");
printf("accept successful !!!n");
char ipbuf[64] = {0};
printf("client || ip: %s, port: %dn",
inet_ntop(AF_INET, &client_addr.sin_addr.s_addr, ipbuf, sizeof(ipbuf)),
ntohs(client_addr.sin_port));
printf("**************************n");
while (1)
{
memset(buffer, 0, sizeof(buffer));
// 接收
int len = recv(conn, buffer, sizeof(buffer), 0);
if (strcmp(buffer, "exit") == 0 || strcmp(buffer, "q") == 0)
break;
if(len > 0)
{
printf("Recv:%s (%d Byte)n", buffer, strlen(buffer));
}
}
close(conn);
close(server_sockfd);
return 0;
}
2-2 client
#include <sys/types.h>
#include <sys/socket.h>
#include <stdio.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/shm.h>
#define PORT 8887
#define BUFFER_SIZE 1024
int main()
{
int sockfd = socket(AF_INET, SOCK_STREAM, 0);
struct sockaddr_in servaddr;
memset(&servaddr, 0, sizeof(servaddr));
servaddr.sin_family = AF_INET;
servaddr.sin_port = htons(PORT);
servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
/// 连接服务器，成功返回0，错误返回-1
if (connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr)) < 0)
{
perror("connect");
exit(1);
}
printf("**************************n");
printf("connect successful !!!n");
char ipbuf[64] = {0};
printf("server || ip: %s, port: %dn",
inet_ntop(AF_INET, &servaddr.sin_addr.s_addr, ipbuf, sizeof(ipbuf)),
ntohs(servaddr.sin_port));
printf("now you can send message to servern");
printf("**************************n");
char sendbuf[BUFFER_SIZE];
while (fgets(sendbuf, sizeof(sendbuf), stdin) != NULL)
{
if(sendbuf[strlen(sendbuf)-1] == 'n')
sendbuf[strlen(sendbuf)-1] = ' ';
// 发送
send(sockfd, sendbuf, strlen(sendbuf), 0);
if (strcmp(sendbuf, "exit") == 0 || strcmp(sendbuf, "q") == 0)
break;
memset(sendbuf, 0, sizeof(sendbuf));
}
close(sockfd);
return 0;
}
2-3 编译和运行测试
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