网络通信1—TCP程序编写步骤（参照 Ubuntu 16.04 版本）

TCP基础模型
服务器流程step 1：创建 socke() 套接字接口并判断

listenfd = socket（AF_INET, SOCK_STREAM, 0）;if (listenfd == -1){perror("socket failed");return -1;}step 2：设置 IP 和 Port
memset (&seraddr, 0, sizeof(seraddr));seraddr.sin_family = AF_INET;seraddr.sin_port = htons(8888);seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");step 3：绑定 IP 和 Port 并判断
ret = bind(listenfd, (struct sockaddr *)&seraddr, sizeof(seraddr));if (ret == -1){perror("bind failed");return -1;}step 4：监听连接并判断
ret = listen(listenfd, 5);if (ret == -1){perror("listen failed");return -1;}step 5：接受连接请求并判断
connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &addrlen);if (connfd == -1){perror("accept failed");return -1;}printf("connect sucessfully: client IP: %s, Port: %d\n", inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port)）;step 6：接收数据并判断
ret = recv(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("recv failed");return -1;}printf("recv from client: %s\nrecv %d bytes\n", buf, ret);step 7：发送数据并判断
ret = send(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("send failed");return -1;}printf("send successfully!\n");step 8：关闭连接
close(connfd);step 9：检查头文件和变量是否定义
客户端流程step 1：创建 socke() 套接字接口并判断
connfd = socket（AF_INET, SOCK_STREAM, 0）;if (connfd == -1){perror("socket failed");return -1;}step 2：设置服务器 IP 和 Port
memset (&seraddr, 0, sizeof(seraddr));seraddr.sin_family = AF_INET;seraddr.sin_port = htons(8888);seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");step 3：发送连接请求并判断
ret = connect(connfd, (struct sockaddr *)&seraddr, sizeof(seraddr));if (ret == -1){perror("connect faile");return -1;}printf("connect sucessfully!\n");step 4：发送数据并判断
ret = send(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("send faile");return -1;}printf("send successfully!");step 5：接收数据
ret = recv(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("recv faile");return -1;}printf("%s\n", buf);step 6：关闭连接
close(connfd);step 7：检查头文件和变量是否定义
TCP 循环服务器模型
服务器流程step 1：创建 socke() 套接字接口并判断

listenfd = socket（AF_INET, SOCK_STREAM, 0）;if (listenfd == -1){perror("socket failed");return -1;}step 2：设置 IP 和 Port
memset (&seraddr, 0, sizeof(seraddr));seraddr.sin_family = AF_INET;seraddr.sin_port = htons(8888);seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");step 3：绑定 IP 和 Port 并判断
ret = bind(listenfd, (struct sockaddr *)&seraddr, sizeof(seraddr));if (ret == -1){perror("bind failed");return -1;}step 4：监听连接并判断
ret = listen(listenfd, 5);if (ret == -1){perror("listen failed");return -1;}step 5：设置循环连接
while(1)step 6：接受连接请求并判断
connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &addrlen);if (connfd == -1){perror("accept failed");return -1;}printf("connect sucessfully: client IP: %s, Port: %d\n", inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port)）;step 7：循环接收数据，直达条件满足退出
while(1)step 8：接收数据并判断
ret = recv(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("recv failed");return -1;}step 9：设置跳出循环的条件
if (!strncmp("quit", buf, 4))break;printf("recv from client: %s\nrecv %d bytes\n", buf, ret);step 10：发送数据并判断
ret = send(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("send failed");return -1;}printf("send successfully!\n");step 11：关闭连接
close(connfd);step 12：检查头文件和变量是否定义
客户端流程step 1：创建 socke() 套接字接口并判断
connfd = socket（AF_INET, SOCK_STREAM, 0）;if (connfd == -1){perror("socket failed");return -1;}step 2：设置服务器 IP 和 Port
memset (&seraddr, 0, sizeof(seraddr));seraddr.sin_family = AF_INET;seraddr.sin_port = htons(8888);seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");step 3：发送连接请求并判断
ret = connect(connfd, (struct sockaddr *)&seraddr, sizeof(seraddr));if (ret == -1){perror("connect faile");return -1;}printf("connect sucessfully!\n");step 4：设置数据循环，并获取标准输入的数据
while (1){fgets(buf, sizeof(buf), stdin);buf[strlen(buf)-1] = '\0';...}step 5：发送数据并判断
ret = send(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("send faile");return -1;}printf("send successfully!");step 6：设置退出条件
if (!strncmp("quit", buf, 4))break;step 7：接收数据
ret = recv(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("recv faile");return -1;}printf("%s\n", buf);step 8：关闭连接
close(connfd);step 9：检查头文件和变量是否定义
TCP 并发服务器模型
服务器流程step 1：创建 socke() 套接字接口并判断

listenfd = socket（AF_INET, SOCK_STREAM, 0）;if (listenfd == -1){perror("socket failed");return -1;}step 2：设置 IP 和 Port
memset (&seraddr, 0, sizeof(seraddr));seraddr.sin_family = AF_INET;seraddr.sin_port = htons(8888);seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");step 3：绑定 IP 和 Port 并判断
ret = bind(listenfd, (struct sockaddr *)&seraddr, sizeof(seraddr));if (ret == -1){perror("bind failed");return -1;}step 4：监听连接并判断
ret = listen(listenfd, 5);if (ret == -1){perror("listen failed");return -1;}step 5：设置信号处理防止僵尸进程
signal(SIGCHLD, SIG_IGN);step 6：设置循环建立连接
while(1)step 7：接受连接请求并判断
connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &addrlen);if (connfd == -1){perror("accept failed");return -1;}printf("connect sucessfully: client IP: %s, Port: %d\n", inet_ntoa(cliaddr.sin_addr), ntohs(cliaddr.sin_port)）;step 8：创建子进程并判断
pid = fork();if (pid == -1){perror("fork create");return -1}step 9：设置父进程关闭连接并重新建立链接
if (pid > 0){close(connfd);continue;}step 10：子进程关闭监听，并循环接收数据
close(listenfd);while(1)step 11：接收数据并判断
ret = recv(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("recv failed");return -1;}step 12：设置跳出循环的条件
if (!strncmp("quit", buf, 4))break;printf("recv from client: %s\nrecv %d bytes\n", buf, ret);step 10：发送数据并判断
ret = send(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("send failed");return -1;}printf("send successfully!\n");step 11：关闭连接同时退出进程
close(connfd);exit(0);step 12：检查头文件和变量是否定义
客户端流程step 1：创建 socke() 套接字接口并判断
connfd = socket（AF_INET, SOCK_STREAM, 0）;if (connfd == -1){perror("socket failed");return -1;}step 2：设置服务器 IP 和 Port
memset (&seraddr, 0, sizeof(seraddr));seraddr.sin_family = AF_INET;seraddr.sin_port = htons(8888);seraddr.sin_addr.s_addr = inet_addr("127.0.0.1");step 3：发送连接请求并判断
ret = connect(connfd, (struct sockaddr *)&seraddr, sizeof(seraddr));if (ret == -1){perror("connect faile");return -1;}printf("connect sucessfully!\n");step 4：设置数据循环，并获取标准输入的数据
while (1){fgets(buf, sizeof(buf), stdin);buf[strlen(buf)-1] = '\0';...}step 5：发送数据并判断
ret = send(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("send faile");return -1;}printf("send successfully!");step 6：设置退出条件
if (!strncmp("quit", buf, 4))break;step 7：接收数据
ret = recv(connfd, buf, sizeof(buf), 0);if (ret == -1){perror("recv faile");return -1;}printf("%s\n", buf);step 8：关闭连接
close(connfd);step 9：检查头文件和变量是否定义