Select实现并发服务器

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并发服务器除了可以用多线程和多进程实现以外，还可以用select实现单线程并发，下面用select实现简单的示例，服务器接收客户端的连接，并将客户发的消息返回，代码如下：

服务器端代码：
main.c

#include <sys/types.h>#include <sys/socket.h>#include <sys/time.h>#include <netinet/in.h>#include <stdarg.h>#include <unistd.h>#include <string.h>#include <stdio.h>#include <errno.h>#define PORT 8888#define BUFF_LEN 1024int client_sock;int errexit(const char *format, ...);int echo(int fd);int main(){    int ss = create_tcp_server(PORT);    if(-1 == ss)        exit(-1);    struct sockaddr_in fsin;    unsigned int alen;    int fd;    fd_set rfds;/* read file descriptor set */    fd_set afds;/* active file descriptor set   */    int nfds = getdtablesize();    FD_ZERO(&afds);    FD_SET(ss, &afds);    while (1) {        memcpy(&rfds, &afds, sizeof(rfds));        if (select(nfds, &rfds, (fd_set *)0, (fd_set *)0, (struct timeval *)0) < 0){            errexit("select: %s\n", strerror(errno));        }        if (FD_ISSET(ss, &rfds)) {            alen = sizeof(fsin);            int ssock = accept(ss, (struct sockaddr *)&fsin, &alen);            if (ssock < 0)                errexit("accept: %s\n", strerror(errno));            else                printf("accept clinet %d\n", ssock);            FD_SET(ssock, &afds);        }        for (fd = 0; fd < nfds; ++fd){            if (fd != ss && FD_ISSET(fd, &rfds)){                if (echo(fd) <= 0) {                    (void) close(fd);                    FD_CLR(fd, &afds);                }            }        }    }}int echo(int fd){    char buf[BUFF_LEN];    int cc = read(fd, buf, sizeof(buf));    if(cc > 0){        printf("recv msg from client %d : %s\n", fd, buf);        if(write(fd, buf, cc) < 0)            printf("write to client %d error, close!\n", fd);    } else if(cc == 0)        printf("client %d disconnect\n", fd);    else        printf("read from client %d error, close!\n", fd);    return cc;}int errexit(const char *format, ...){    va_list args;    va_start(args, format);    vfprintf(stderr, format, args);    va_end(args);    exit(1);}

CreateServer.h//封装了创建服务器代码

#ifndef CREATESERVER_H#define CREATESERVER_Hint create_tcp_server(int);int create_udp_server(int);#endif // CREATESERVER_H

CreateServer.c//封装方法的具体实现

#include <sys/types.h>#include <sys/socket.h>#include <arpa/inet.h>#define LISTEN_SIZE 20int start_server(int port, int type){    //建立服务器套接字    int ss = socket(AF_INET, type, 0);    if(ss < 0){        printf("create socket error\n");        return -1;    }    //设置服务器地址    struct sockaddr_in server_addr; //服务器地址结构    bzero(&server_addr, sizeof(struct sockaddr_in)); //清零    server_addr.sin_family = AF_INET; //协议族    server_addr.sin_addr.s_addr = htonl(INADDR_ANY); //ip地址    server_addr.sin_port = htons(port); //端口    //绑定地址结构到套接字描述符    if(bind(ss, (struct sockaddr*)&server_addr, sizeof(server_addr)) < 0){        printf("bind error\n");        return -1;    }    //TCP    if(SOCK_STREAM == type){        //设置侦听        if(listen(ss, LISTEN_SIZE) < 0){            printf("listen error\n");            return -1;        }        printf("tcp server start\n");    }    else        printf("udp server start\n");    return ss;}int create_tcp_server(int port){    start_server(port, SOCK_STREAM);}int create_udp_server(int port){    start_server(port, SOCK_DGRAM);}

客户端测试代码：
代码同之前的博客，参见：http://blog.csdn.net/wanna_wsl/article/details/53712066

源码下载地址：
https://github.com/Wushaoling/Linux-C-Socket/tree/master/TCP/TCP%E7%AE%80%E5%8D%95%E6%95%B0%E6%8D%AE%E5%8F%91%E9%80%81

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