使用select函数提高服务器的处理能力

server.cpp

#include <sys/types.h>
#include <netinet/in.h>
#include <unistd.h>
#include <arpa/inet.h>
//#include <windows.h>
#include <sys/socket.h>
//#include <winsock.h>

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <strings.h>
//#include <sys/wait.h>
#include <errno.h>

#define DEFAULT_PORT 6666
int main(int argc,char ** argv)
{
    int serverfd,acceptfd;/*监听socket:serverfd,数据传输socket:acceptfd*/
    struct sockaddr_in my_addr;/*本机地址信息*/
    struct sockaddr_in their_addr;/*客户地址信息*/
    unsigned int sin_size,myport = 6666,lisnum = 10;
    if((serverfd = socket(AF_INET,SOCK_STREAM,0)) == -1){
        perror("socket");
        return -1;
    }
    printf("socket ok! 
");
    my_addr.sin_family = AF_INET;
    my_addr.sin_port = htons(DEFAULT_PORT);
    my_addr.sin_addr.s_addr = INADDR_ANY;
    bzero(&(my_addr.sin_zero),0);
    if(bind(serverfd,(struct sockaddr *)&my_addr,sizeof(struct sockaddr))==-1){
        perror("bind");
        return -2;
    }
    printf("bind OK!
");
    if(listen(serverfd,lisnum)==-1){
        perror("listen");
        return -3;
    }
    printf("listen OK!
");
    
    fd_set client_fdset;/*监控文件描述符集合*/
    int maxsock;        /*监控文件描述符中最大的文件号*/
    struct timeval tv;  /*超时返回时间*/
    int client_sockfd[5];/*存放活动的sockfd*/
    bzero((void*)client_sockfd,sizeof(client_sockfd));
    int conn_amount = 0; /*用来记录描述符数量*/
    maxsock = serverfd;
    char buffer[1024];
    int ret = 0;
    while(1){
        /*初始化文件描述符到集合*/
        FD_ZERO(&client_fdset);
        /*加入服务器描述符*/
        FD_SET(serverfd,&client_fdset);
        /*设置超时时间*/
        tv.tv_sec = 30;/*30秒*/
        tv.tv_usec = 0;
        /*把活动的句柄加到文件描述符中*/
        for(int i = 0; i < 5; i++){
            /*程序中Listen 中参数设置为5，故i要小于5*/
            if(client_sockfd[i]!=0){
                FD_SET(client_sockfd[i],&client_fdset);
            }
        }
        /*select函数*/
        ret = select(maxsock+1,&client_fdset,NULL,NULL,&tv);
        if(ret < 0){
            perror("select error!
");
            break;
        }
        else if(ret == 0){
            printf("timeout
");
            continue;
        }
        /*轮询各个文件描述符*/
        for(int i = 0; i < conn_amount; i++){
           /* FD_ISSET检查是否client_sockfd是否可读写，>0可读写*/
           if(FD_ISSET(client_sockfd[i],&client_fdset)){  
               printf("start recv from client[%d]:
",i);
               ret = recv(client_sockfd[i],buffer,1024,0);
               if(ret <= 0){
                   printf("client[%d] close
",i);
                   close(client_sockfd[i]);
                   FD_CLR(client_sockfd[i],&client_fdset);
                   client_sockfd[i] = 0;
                }
                else{
                    printf("recv from client[%d]: %s
",i,buffer);
                }
            }
        }
        /*检查是否有新的连接，如果有，接收连接，加入到client_sockfd中*/
        if(FD_ISSET(serverfd,&client_fdset)){
            /*接受连接*/
            struct sockaddr_in client_addr;
            size_t size = sizeof(struct sockaddr_in);
            int sock_client = accept(serverfd,(struct sockaddr*)(&client_addr),(unsigned int*)(&size));
            if(sock_client <0){
                perror("accept error!
");
                continue;
            }
            /*把连接加入到文件描述符集合中*/
            if(conn_amount < 5){
                client_sockfd[conn_amount++] = sock_client;
                bzero(buffer,1024);
                strcpy(buffer,"this is a server!welcome!
");
                send(sock_client,buffer,1024,0);
                printf("new connection client[%d] %s:%d
",conn_amount,inet_ntoa(client_addr.sin_addr),ntohs(client_addr.sin_port));
                bzero(buffer,sizeof(buffer));
                ret = recv(sock_client,buffer,1024,0);
                if(ret < 0){
                    perror("recv error!
");
                    close(serverfd);
                    return -1;
                }
                printf("recv: %s
",buffer);
                if(sock_client > maxsock){
                    maxsock = sock_client;
                }
                else{
                    printf("max connection !!!quit!!
");
                    break;
                }
            }
        }
    }
    for(int i = 0; i < 5; i++){
        if(client_sockfd[i] != 0){
            close(client_sockfd[i]);
        }
    }
    close(serverfd);
    return 0;
}

 Client.cpp

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
//#include <winsock.h>
#include <netinet/in.h>
#include <arpa/inet.h>
//#include <windows.h>
#include <errno.h>
#define DEFAULT_PORT 6666


int main(int argc,char *argv[])
{
    int connfd = 0;
    int cLen = 0;
    struct sockaddr_in client;
    if(argc < 2){
        printf(" Uasge: clientent [server IP address]
");
        return -1;
    }
    client.sin_family = AF_INET;
    client.sin_port = htons(DEFAULT_PORT);
    client.sin_addr.s_addr = inet_addr(argv[1]);
    connfd = socket(AF_INET,SOCK_STREAM,0);
    if(connfd < 0){
        perror("socket");
        return -1;
    }
    if(connect(connfd,(struct sockaddr*)&client,sizeof(client))<0){
        perror("connect");
        return -1;
    }
    char buffer[1024];
    bzero(buffer,sizeof(buffer));
    recv(connfd,buffer,1024,0);
    printf("recv: %s
",buffer);
    bzero(buffer,sizeof(buffer));
    strcpy(buffer,"this is client!
");
    send(connfd,buffer,1024,0);
    while(1){
        bzero(buffer,sizeof(buffer));
        scanf("%s",buffer);
        int p =strlen(buffer);
        buffer[p] = '';
        send(connfd,buffer,1024,0);
        printf("i have send a buffer!
");
    }
    close(connfd);
    return 0;
}

 makefile

all:server client
server:server.o
    g++ -g -o server server.o
client:client.o
    g++ -g -o client client.o
server.o:server.cpp
    g++ -g -c server.cpp
client.o:client.cpp
    g++ -g -c client.cpp
clean:all
    rm all