本文就是在windows下进行socket编程，搭建一个TCP客户端。
在visual studio下编程，首先在windows下进行初始化（这点在linux下是不需要的）：
/* 初始化 Winsock */ #include<stdio.h> #include<winsock2.h> #pragma comment(lib,"ws2_32.lib") int main(int argc, char *argv[]) { WSADATA wsa; printf(" 初始化中Initialising Winsock..."); if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0)//Winsock 启动或初始化winsock库，第一个为加载的版本，第二个为WSADATA结构 //WSAStartup应该与WSACleanup成对使用，WSAStartup的功能是初始化Winsock DLL，WSACleanup是来解除与Socket库的绑定并且释放Socket库所占用的系统资源。 { printf("Failed. Error Code : %d", WSAGetLastError()); return 1; } printf("初始化成功Initialised."); return 0; }
运行结果：
可以看出winsock的环境已经搭建完成了。
下面就是创建一个套接字：
/* Create a TCP socket */ #include<stdio.h> #include<winsock2.h> #pragma comment(lib,"ws2_32.lib") //Winsock Library int main(int argc, char *argv[]) { WSADATA wsa; SOCKET s; printf(" 初始化Initialising Winsock..."); if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) { printf("失败Failed. Error Code : %d", WSAGetLastError()); return 1; } printf("Initialised. "); if ((s = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) //函数socket()创建一个套接字并返回一个可用于其他网络命令的套接字描述符。 /* 地址系列：AF_INET（这是IP版本4） 类型：SOCK_STREAM（这意味着面向连接的TCP协议） 协议：0 [或IPPROTO_TCP，IPPROTO_UDP] */ { printf("创建失败Could not create socket : %d", WSAGetLastError()); } printf("成功Socket created. "); return 0; }
好的，此时我们已经成功地创建了一个套接字。
下面就是通过bind绑定套接字：
#include<stdio.h> #include<winsock2.h> #pragma comment(lib,"ws2_32.lib") //Winsock Library int main(int argc, char *argv[]) { WSADATA wsa; SOCKET s; struct sockaddr_in server; printf(" Initialising Winsock..."); if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) { printf("Failed. Error Code : %d", WSAGetLastError()); return 1; } printf("Initialised. "); //Create a socket if ((s = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) { printf("Could not create socket : %d", WSAGetLastError()); } printf("Socket created. "); //配置sockaddr_in 结构体 server.sin_family = AF_INET; server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons(8888); //Bind if (bind(s, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR) { printf("Bind failed with error code : %d", WSAGetLastError()); } puts("Bind done"); closesocket(s); return 0; }
进行调试编译，结果如下：
现在，绑定完成了，它的时间让套接字监听连接。我们将套接字绑定到特定的IP地址和特定的端口号。通过这样做，我们确保所有到这个端口号的传入数据都被这个应用程序接收。
下面进行listen对端口监听，然后accept接收得到的数据。
/* Bind socket to port 8888 on localhost */ #include<stdio.h> #include<winsock2.h> #pragma comment(lib,"ws2_32.lib") //Winsock Library int main(int argc, char *argv[]) { WSADATA wsa; SOCKET s, new_socket; struct sockaddr_in server, client; int c; printf(" Initialising Winsock..."); if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) { printf("Failed. Error Code : %d", WSAGetLastError()); return 1; } printf("Initialised. "); //Create a socket if ((s = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) { printf("Could not create socket : %d", WSAGetLastError()); } printf("Socket created. "); //Prepare the sockaddr_in structure server.sin_family = AF_INET; server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons(8888); //Bind if (bind(s, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR) { printf("Bind failed with error code : %d", WSAGetLastError()); } puts("Bind done"); //Listen to incoming connections if (listen(s, 3) != 0) { printf("listen is error"); } //Accept and incoming connection puts("Waiting for incoming connections..."); c = sizeof(struct sockaddr_in); new_socket = accept(s, (struct sockaddr *)&client, &c); if (new_socket == INVALID_SOCKET) { printf("accept failed with error code : %d", WSAGetLastError()); } puts("Connection accepted"); closesocket(s); WSACleanup(); return 0; }
此时，一个客户端就搭建完成了，下面通过软件对客户端进行实验验证。
创建一个客户端
创建完成后运行称程序，点击连接按钮，可以看到如下输出
上面我们接受了一个传入的连接，但立即关闭。这不是很有成效。传入连接建立后，可以做很多事情。毕竟连接是为了沟通的目的而建立的。所以让我们用send函数回复客户。
/* Bind socket to port 8888 on localhost */ #include<io.h> #include<stdio.h> #include<winsock2.h> #pragma comment(lib,"ws2_32.lib") //Winsock Library int main(int argc, char *argv[]) { WSADATA wsa; SOCKET s, new_socket; struct sockaddr_in server, client; int c; char *message; printf(" Initialising Winsock..."); if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) { printf("Failed. Error Code : %d", WSAGetLastError()); return 1; } printf("Initialised. "); //Create a socket if ((s = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) { printf("Could not create socket : %d", WSAGetLastError()); } printf("Socket created. "); //Prepare the sockaddr_in structure server.sin_family = AF_INET; server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons(8888); //Bind if (bind(s, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR) { printf("Bind failed with error code : %d", WSAGetLastError()); } puts("Bind done"); //Listen to incoming connections listen(s, 3); //Accept and incoming connection puts("Waiting for incoming connections..."); c = sizeof(struct sockaddr_in); new_socket = accept(s, (struct sockaddr *)&client, &c); if (new_socket == INVALID_SOCKET) { printf("accept failed with error code : %d", WSAGetLastError()); } puts("Connection accepted"); //Reply to client message = "Hello Client , I have received your connection. But I have to go now, bye "; send(new_socket, message, strlen(message), 0); getchar(); closesocket(s); WSACleanup(); return 0; }
同样运行程序，然后点击连接，可以看到调试软件有如下的反馈输出：
虽然有反馈了但是对客户端发送过来的数据没有recv进行显示处理，這里，将整个程序优化如下：
/* TCP Echo server example in winsock Live Server on port 8888 */ #include<stdio.h> #include<winsock2.h> #pragma comment(lib, "ws2_32.lib") //Winsock Library int main(int argc, char *argv[]) { WSADATA wsa; SOCKET master, new_socket, client_socket[30], s; struct sockaddr_in server, address; int max_clients = 30, activity, addrlen, i, valread; char *message = "ECHO Daemon v1.0 "; //size of our receive buffer, this is string length. int MAXRECV = 1024; //set of socket descriptors fd_set readfds; //1 extra for null character, string termination char *buffer; buffer = (char*)malloc((MAXRECV + 1) * sizeof(char)); for (i = 0; i < 30; i++) { client_socket[i] = 0; } printf(" Initialising Winsock..."); if (WSAStartup(MAKEWORD(2, 2), &wsa) != 0) { printf("Failed. Error Code : %d", WSAGetLastError()); exit(EXIT_FAILURE); } printf("Initialised. "); //Create a socket if ((master = socket(AF_INET, SOCK_STREAM, 0)) == INVALID_SOCKET) { printf("Could not create socket : %d", WSAGetLastError()); exit(EXIT_FAILURE); } printf("Socket created. "); //Prepare the sockaddr_in structure server.sin_family = AF_INET; server.sin_addr.s_addr = INADDR_ANY; server.sin_port = htons(8888); //Bind if (bind(master, (struct sockaddr *)&server, sizeof(server)) == SOCKET_ERROR) { printf("Bind failed with error code : %d", WSAGetLastError()); exit(EXIT_FAILURE); } puts("Bind done"); //Listen to incoming connections listen(master, 3); //Accept and incoming connection puts("Waiting for incoming connections..."); addrlen = sizeof(struct sockaddr_in); while (TRUE) { //clear the socket fd set FD_ZERO(&readfds); //add master socket to fd set FD_SET(master, &readfds); //add child sockets to fd set for (i = 0; i < max_clients; i++) { s = client_socket[i]; if (s > 0) { FD_SET(s, &readfds); } } //wait for an activity on any of the sockets, timeout is NULL , so wait indefinitely activity = select(0, &readfds, NULL, NULL, NULL); if (activity == SOCKET_ERROR) { printf("select call failed with error code : %d", WSAGetLastError()); exit(EXIT_FAILURE); } //If something happened on the master socket , then its an incoming connection if (FD_ISSET(master, &readfds)) { if ((new_socket = accept(master, (struct sockaddr *)&address, (int *)&addrlen))<0) { perror("accept"); exit(EXIT_FAILURE); } //inform user of socket number - used in send and receive commands printf("New connection , socket fd is %d , ip is : %s , port : %d ", new_socket, inet_ntoa(address.sin_addr), ntohs(address.sin_port)); //send new connection greeting message if (send(new_socket, message, strlen(message), 0) != strlen(message)) { perror("send failed"); } puts("Welcome message sent successfully"); //add new socket to array of sockets for (i = 0; i < max_clients; i++) { if (client_socket[i] == 0) { client_socket[i] = new_socket; printf("Adding to list of sockets at index %d ", i); break; } } } //else its some IO operation on some other socket :) for (i = 0; i < max_clients; i++) { s = client_socket[i]; //if client presend in read sockets if (FD_ISSET(s, &readfds)) { //get details of the client getpeername(s, (struct sockaddr*)&address, (int*)&addrlen); //Check if it was for closing , and also read the incoming message //recv does not place a null terminator at the end of the string (whilst printf %s assumes there is one). valread = recv(s, buffer, MAXRECV, 0); if (valread == SOCKET_ERROR) { int error_code = WSAGetLastError(); if (error_code == WSAECONNRESET) { //Somebody disconnected , get his details and print printf("Host disconnected unexpectedly , ip %s , port %d ", inet_ntoa(address.sin_addr), ntohs(address.sin_port)); //Close the socket and mark as 0 in list for reuse closesocket(s); client_socket[i] = 0; } else { printf("recv failed with error code : %d", error_code); } } if (valread == 0) { //Somebody disconnected , get his details and print printf("Host disconnected , ip %s , port %d ", inet_ntoa(address.sin_addr), ntohs(address.sin_port)); //Close the socket and mark as 0 in list for reuse closesocket(s); client_socket[i] = 0; } //Echo back the message that came in else { //add null character, if you want to use with printf/puts or other string handling functions buffer[valread] = ' '; printf("%s:%d - %s ", inet_ntoa(address.sin_addr), ntohs(address.sin_port), buffer); send(s, buffer, valread, 0); } } } } closesocket(s); WSACleanup(); return 0; }
运行，程序，打开仿真软件配置后点击连接，可以看到输入如下
输入数据点击发送后可以看到，输出如下：
至此，一个功能基本完备的服务器已经搭建完成了，但是其实这个服务器还是不完善的，这个将在下片文章中进行说明。
下篇文章：