综合unp前五章，写了一个服务器-客户端程序。
主要功能：客户端从标准输入读入字符串发送到服务器，服务器显示。服务器接受连接后，fork()子进程实现具体操作。
服务器主要过程：
socket()->bind()->listen()->accept()->read()
客户端：
socket()->connect()->write()
测试结果：
（1）新建服务器、客户端
zy@zy-virtual-machine:~$ lsof -i COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME server 16423 zy 3u IPv4 173909 0t0 TCP *:9999 (LISTEN) client 16425 zy 3u IPv4 172544 0t0 TCP localhost:44896->localhost:9999 (ESTABLISHED) server 16426 zy 4u IPv4 173910 0t0 TCP localhost:9999->localhost:44896 (ESTABLISHED)
server的父进程处于监听状态，子进程和client处于建立连接状态。
（2）传数据，client发送“OFF”表示关闭连接
zy@zy-virtual-machine:~/practice/tcp$ ./client socket hello OFF zy@zy-virtual-machine:~/practice/tcp$ ./server server ip is 0.0.0.0 running on port 9999 connction from 127.0.0.1, port 44896 socket hello
（3）关闭连接后的端口状态
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zy@zy-virtual-machine:~$ lsof -i COMMAND PID USER FD TYPE DEVICE SIZE/OFF NODE NAME server 16423 zy 3u IPv4 173909 0t0 TCP *:9999 (LISTEN)
服务器代码：
1 #include <stdio.h> 2 #include <sys/socket.h> 3 #include <sys/types.h> 4 #include <arpa/inet.h> 5 #include <netinet/in.h> 6 #include <unistd.h> 7 #include <string.h> 8 #include <stdlib.h> 9 10 11 void foo(struct sockaddr_in addr, int fd) { 12 char buff[1024]; 13 char c; 14 int i; 15 int len; 16 inet_ntop(AF_INET, &addr.sin_addr, buff, sizeof(buff)); 17 printf("connction from %s, port %d\n", buff, ntohs(addr.sin_port)); 18 while(1) { 19 i = 0; 20 c = '0'; 21 while (i < 1024 && c != '\0') { 22 len = read(fd, (void*)&c, 1); 23 if (len > 0) { 24 buff[i++] = c; 25 } 26 } 27 buff[i] = '\0'; 28 if (i > 1) { 29 if (strcmp(buff, "OFF") == 0){ 30 break; 31 } 32 printf("%s\n", buff); 33 } 34 sleep(1); 35 } 36 exit(0); 37 } 38 int main() { 39 pid_t pid; 40 int serverfd, clientfd; 41 struct sockaddr_in serveraddr, clientaddr; 42 socklen_t clientaddr_len; 43 u_short port = 9999; 44 char buff[1024]; 45 serverfd = socket(AF_INET, SOCK_STREAM, 0); 46 if (serverfd == -1) { 47 printf("socket error\n"); 48 exit(0); 49 } 50 bzero(&serveraddr, sizeof(serveraddr)); 51 serveraddr.sin_family = AF_INET; 52 serveraddr.sin_port = htons(port); 53 serveraddr.sin_addr.s_addr = htonl(INADDR_ANY); 54 if (bind(serverfd, (struct sockaddr *)&serveraddr, sizeof(serveraddr)) == -1) { 55 printf("bind error\n"); 56 exit(0); 57 } 58 inet_ntop(AF_INET, &serveraddr.sin_addr, buff, sizeof(buff)); 59 printf("server ip is %s running on port %d\n", buff, ntohs(serveraddr.sin_port)); 60 61 if ( listen(serverfd, 1) == -1 ) { 62 printf("listen error\n"); 63 exit(0); 64 } 65 while(1) { 66 clientaddr_len = sizeof(clientaddr); 67 clientfd = accept(serverfd, (struct sockaddr *)&clientaddr, &clientaddr_len); 68 if ((pid = fork()) == 0) { 69 close(serverfd); 70 foo(clientaddr, clientfd); 71 close(clientfd); 72 exit(0); 73 } 74 close(clientfd); 75 } 76 close(serverfd); 77 exit(0); 78 }
客户端代码：
1 #include <stdio.h> 2 #include <sys/socket.h> 3 #include <sys/types.h> 4 #include <arpa/inet.h> 5 #include <netinet/in.h> 6 #include <unistd.h> 7 #include <string.h> 8 #include <stdlib.h> 9 10 int main() { 11 int clientfd; 12 struct sockaddr_in clientaddr; 13 char buff[1024]; 14 int i; 15 clientfd = socket(AF_INET, SOCK_STREAM, 0); 16 if (clientfd == -1) { 17 printf("socket error\n"); 18 exit(0); 19 } 20 clientaddr.sin_family = AF_INET; 21 clientaddr.sin_addr.s_addr = inet_addr("127.0.0.1"); 22 clientaddr.sin_port = htons(9999); 23 if (connect(clientfd, (struct sockaddr *)&clientaddr, sizeof(clientaddr)) == -1) { 24 printf("connet error\n"); 25 exit(0); 26 } 27 while (1) { 28 gets(buff); 29 i = 0; 30 do{ 31 write(clientfd, (void*)&buff[i], 1); 32 } while (buff[i++] != '\0'); 33 if (strcmp(buff, "OFF") == 0){ 34 break; 35 } 36 } 37 close(clientfd); 38 exit(0); 39 }