Select实现并发服务器

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 
#include 
#include 
#include 
#include 

#include 
#include 
#include 
#include 

#define PORT 8888
#define BUFF_LEN 1024

int 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_H

int create_tcp_server(int);
int create_udp_server(int);

#endif // CREATESERVER_H

CreateServer.c//封装方法的具体实现

#include 
#include 
#include 
#define LISTEN_SIZE 20

int 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