I/O复用(select)——回声服务器端/客户端

一、select

　　使用select函数可以将多个文件描述符集中到一起统一监视，监视事件如下：

• 是否存在待读取数据。
• 是否可传输无阻塞传输数据。
• 是否发生异常。

　　将关心上述3种事件的文件描述发分别注册到对应参数(readfds,writefds,exceptfds)中去。

　　int select(int nfds, fd_set FAR * readfds, fd_set FAR * writefds, fd_set FAR * exceptfds, const struct timeval FAR * timeout);

1、linux

服务器端：

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>

 #define BUF_SIZE 1024
 void error_handling(char * messages);

 int main(int argc, char *argv[])
 {
     if(argc != )
     {
         printf("Usage : %s <port>\n", argv[]);
         exit();
     }
     int serverSock, clientSock;
     struct sockaddr_in serverAddr, clientAddr;
     socklen_t clientAddrSize;

     struct timeval timeout;
     fd_set reads, cpy_reads;
     int fd_max, fd_num;

     char message[BUF_SIZE];
     int strLen;

     serverSock =socket(PF_INET, SOCK_STREAM, );
     if(serverSock == -)
         error_handling("socket() error");

     memset(&serverAddr, , sizeof(serverAddr));
     serverAddr.sin_family = AF_INET;
     serverAddr.sin_addr.s_addr = htonl(INADDR_ANY);
     serverAddr.sin_port = htons(atoi(argv[]));

     if(bind(serverSock, (struct sockaddr*) &serverAddr, sizeof(serverAddr)) == -)
         error_handling("bind() error");
     if(listen(serverSock, ) == -)
         error_handling("listen() error");

     FD_ZERO(&reads);
     FD_SET(serverSock, &reads);
     fd_max = serverSock;

     puts("Server start...");
     while(){
         cpy_reads = reads;
         timeout.tv_sec = ;
         timeout.tv_usec = ;

         if((fd_num = select(fd_max+, &cpy_reads, , , &timeout)) == -){
             error_handling("select() error");
             break;
         }
         if(fd_num == ) continue;
         for(int i = ; i <= fd_max; i++){
             if(FD_ISSET(i, &cpy_reads)){
                 if(i == serverSock){ // connection request
                     clientAddrSize = sizeof(clientAddr);
                     clientSock = accept(serverSock, (struct sockaddr*)&clientAddr, &clientAddrSize);
                     FD_SET(clientSock, &reads);
                     if(fd_max < clientSock)
                         fd_max = clientSock;
                     printf("connected client: %d\n", clientSock);
                 }
                 else{ // read message
                     strLen = read(i, message, BUF_SIZE);
                     if(strLen == ){
                         FD_CLR(i, &reads);
                         close(i);
                         printf("close client: %d\n", i);
                     }
                     else{
                         write(i, message, strLen);
                         printf("echo: %d\n",i);
                     }
                 }
             }
         }
     }
     close(serverSock);
     puts("Server close...");
     return ;
 }

 void error_handling(char * messages)
 {
     puts(messages);
     exit();
 }

客户端：

 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <unistd.h>
 #include <arpa/inet.h>
 #include <sys/socket.h>

 #define BUF_SIZE 1024
 void error_handling(char * messages);

 int main(int argc, char *argv[])
 {
     if(argc != )
     {
         printf("Usage : %s <IP> <port>\n", argv[]);
         exit();
     }
     int sock;
     struct sockaddr_in serv_addr;
     char message[BUF_SIZE];
     int strLen;

     sock = socket(PF_INET, SOCK_STREAM, );
     if(sock == -)
         error_handling("socket() error");

     memset(&serv_addr, , sizeof(serv_addr));
     serv_addr.sin_family = AF_INET;
     serv_addr.sin_addr.s_addr = inet_addr(argv[]);
     serv_addr.sin_port = htons(atoi(argv[]));

     if(connect(sock, (struct sockaddr*) &serv_addr, sizeof(serv_addr)) == -)
         error_handling("connect() error");
     else
         puts("Connected...");
     while(){
         puts("Input message(Q to quit):");
         fgets(message, BUF_SIZE, stdin);
         if(!strcmp(message, "q\n") || !strcmp(message, "Q\n"))
             break;

         strLen=strlen(message);
         write(sock, message, strlen(message));
         int recvLen = ;
         while(recvLen < strLen){
             int recvCnt = read(sock, &message[recvLen], BUF_SIZE-);
             if(recvCnt == -)
                 error_handling("read() error");
             recvLen+=recvCnt;
         }
         message[recvLen]=;
         printf("Message from server: %s\n", message);
     }
     close(sock);
     return ;
 }

 void error_handling(char * messages)
 {
     puts(messages);
     exit();
 }

2、windows

服务器端：

 #include <stdio.h>
 #include <stdlib.h>
 #include <WinSock2.h>

 #define BUF_SIZE 1024
 void ErrorHandling(char *message);

 int main(int argc, char *argv[])
 {
     if (argc != ) {
         printf("Usage : %s <port>\n", argv[]);
         exit();
     }

     WSADATA wsa_data;
     SOCKET server_sock, client_sock;
     SOCKADDR_IN server_addr, client_addr;
     TIMEVAL time_out;
     fd_set reads, temp_reads;

     int addr_size;
     int str_len, fd_num;
     char buf[BUF_SIZE];

     if (WSAStartup(MAKEWORD(, ), &wsa_data) != )
         ErrorHandling("WSAStartup() error.");

     server_sock = socket(PF_INET, SOCK_STREAM, );
     if (server_sock == INVALID_SOCKET)
         ErrorHandling("socket() error.");

     memset(&server_addr, , sizeof(server_addr));
     server_addr.sin_family = AF_INET;
     server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
     server_addr.sin_port = htons(atoi(argv[]));

     if (bind(server_sock, (SOCKADDR*)&server_addr, sizeof(server_addr)) == SOCKET_ERROR)
         ErrorHandling("bind() error.");
     if (listen(server_sock, ) == SOCKET_ERROR)
         ErrorHandling("listen() error.");
     printf("Server start...\n");
     FD_ZERO(&reads);
     FD_SET(server_sock, &reads);
     while (true)
     {
         temp_reads = reads;
         time_out.tv_sec = ;
         time_out.tv_usec = ;
         if ((fd_num = select(, &temp_reads, , , &time_out)) == SOCKET_ERROR)
             break;
         if (fd_num == )
             continue;
         for (int i = ; i < reads.fd_count; ++i)
         {
             if (FD_ISSET(reads.fd_array[i], &temp_reads))
             {
                 if (reads.fd_array[i] == server_sock) // connection request
                 {
                     addr_size = sizeof(client_addr);
                     client_sock = accept(server_sock, (SOCKADDR*)&client_addr, &addr_size);
                     if (client_sock == INVALID_SOCKET)
                         ErrorHandling("accept() error.");
                     FD_SET(client_sock, &reads);
                     printf("connected client: %d\n", client_sock);
                 }
                 else // read message
                 {
                     str_len = recv(reads.fd_array[i], buf, BUF_SIZE - , );
                     if (str_len == )
                     {
                         FD_CLR(reads.fd_array[i], &reads);
                         closesocket(temp_reads.fd_array[i]);
                         printf("close client: %d\n", temp_reads.fd_array[i]);
                     }
                     else
                     {
                         send(reads.fd_array[i], buf, str_len, ); // echo
                     }
                 }
             }
         }
     }
     closesocket(server_sock);
     WSACleanup();
     printf("Server end...\n");
     return ;
 }

 void ErrorHandling(char *message) {
     fputs(message, stderr);
     fputc('\n', stderr);
 }

客户端：

 #pragma warning(disable:4996)
 #include <stdio.h>
 #include <stdlib.h>
 #include <string.h>
 #include <winsock2.h>

 #define BUF_SIZE 1024
 void ErrorHandling(char *message);

 int main(int argc, char* argv[]) {
     if (argc != ) {
         printf("Usage : %s <IP> <port>\n", argv[]);
         exit();
     }

     WSADATA wsaData;
     SOCKET sock;
     SOCKADDR_IN serverAddr;
     char message[BUF_SIZE];
     int sLen, recvLen;

     if (WSAStartup(MAKEWORD(, ), &wsaData) != )
         ErrorHandling("WSAStartup() error");

     sock = socket(PF_INET, SOCK_STREAM, );
     if (sock == INVALID_SOCKET)
         ErrorHandling("socket() error");

     memset(&serverAddr, , sizeof(serverAddr));
     serverAddr.sin_family = AF_INET;
     serverAddr.sin_addr.s_addr = inet_addr(argv[]);
     serverAddr.sin_port = htons(atoi(argv[]));

     if (connect(sock, (SOCKADDR*)&serverAddr, sizeof(serverAddr)) == SOCKET_ERROR)
         ErrorHandling("connect() error");
     else
         printf("Connected.......\n");
     while ()
     {
         fputs("Input message(Q to quit):", stdout);
         fgets(message, BUF_SIZE, stdin);
         if (!strcmp(message, "q\n") || !strcmp(message, "Q\n"))
             break;
         sLen = send(sock, message, strlen(message), );
         recvLen = ;
         while (recvLen < sLen) {
             int cnt = recv(sock, message, BUF_SIZE - , );
             if (cnt == -)
                 ErrorHandling("ercv() error");
             recvLen += cnt;
         }
         message[recvLen] = ;
         printf("Message from server: %s\n", message);
     }
     closesocket(sock);
     WSACleanup();
     return ;
 }

 void ErrorHandling(char *message) {
     fputs(message, stderr);
     fputc('\n', stderr);
 }