基于TCP的C/S初级网络编程2

导读

本篇文章对[http://daoluan.github.io/blog/?p=774](http://daoluan.github.io/blog/?p=774)中的“计算器”进行改进，与大家分享。

上面那篇中的服务端属重复型，即一个时刻只处理一客户的请求，处理期间不搭理其他客户。此篇对上篇的“计算器”进行小小的改进——能够接受多个客户的请求。

改进细则：

  1. 独立bind，listen，accept，serve（即calc过程）功能模块；

  2. 所有错误成功提示提取至各功能模块（函数）之外，错误/成功根据各函数的返回值判断（这更符合UNIX编程风范）；

  3. 客户的服务过程由产生的子进程负责。

缺陷：由子进程来负责serve的部分。服务器主进程（父进程）不负责等待子进程结束，资源由内核回收（这一要非必要）。

上实验结果图片解解馋

服务器启动

客户端方面，将client1、client2和client3（编译链接自同一个代码）写进脚本。运行

服务端服务多个客户请求

client

#include <stdio.h>
#include <unistd.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <netinet/ip.h>
#include <arpa/inet.h>
#include <string.h>
#include <string.h>

#define MAXSLEEP 1024

int connect_retry(int sockfd,const struct sockaddr * addr,socklen_t alen)
{
    int nsec;

    printf("connecting\n");
    for(nsec = 1; nsec <= MAXSLEEP; nsec<<=1)
    {
        if(connect(sockfd,addr,alen) == 0)
        {
            printf("connected\n");
            return 0;
        }// if
        if(nsec <= MAXSLEEP/2)//    delay
            sleep(nsec);
    }// for:
    return 0;
}

int main(int argc,char * argv[])
{
    if(argc != 4)
    {
        printf("you must input 4 arg\n");
        return 1;
    }// if

    int fd;    
    struct sockaddr_in si,server;
    char addr[20],buf[20],bufrecv[20];

    bzero(bufrecv,sizeof(bufrecv));
    sprintf(addr,"127.0.0.1");

    fd = socket(AF_INET,SOCK_STREAM,0);//   create socker fd;
    printf("socket ok\n");

//prepare server addr
    bzero(&server,sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(6000);
    inet_pton(AF_INET,addr,(void *)&server.sin_addr);
    printf("server ok\n");

//prepare request data
    bzero(buf,sizeof(buf));
    sprintf(buf,"%c%c%c",argv[1][0],argv[2][0],argv[3][0]);

//connect
    if(connect_retry(fd,(struct sockaddr *)&server,sizeof(server)) < 0)
    {
        printf("connect error\n");
        return 1;
    }// if

//send
    if(send(fd,buf,20,0) < 0) 
    {
        printf("client send error\n");
        return 1;
    }// if

//select
    fd_set readfd;
    FD_ZERO(&readfd);
    FD_SET(fd,&readfd);
    int t;

    if((t = select(FD_SETSIZE,&readfd,NULL,NULL,NULL)) < 0)
    {
        printf("select error\n");
        return 1;
    }// if

//recv
    bzero(bufrecv,sizeof(bufrecv));
    recv(fd,bufrecv,20,0);
    printf("%s\n",bufrecv);

    close(fd);
    return 0;
}

server

#include <stdio.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <errno.h>
#include <ctype.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>

char bufret[20];

int initserver(int type,const struct sockaddr * addr,socklen_t alen,int qlen)
{
    int fd;
    int err = 0;

    if((fd = socket(addr->sa_family,type,0)) < 0)
        return -1;

    printf("binding\n");
    if(bind(fd,addr,alen) < 0)
    {
        err = errno;
        goto errout;
    }// if
    printf("bind succeed \n");

    if(type == SOCK_STREAM || type == SOCK_SEQPACKET)
    {
        printf("listening\n");
        if(listen(fd,1) < 0)
        {
            err = errno;
            printf("listen error\n");
            goto errout;
        }// if
    }// if
    printf("listened \n");
    return (fd);

errout:
    close(fd);
    errno = err;
    return -1;
}

int serve(int sockfd)
{
    int a,b;
    char op,buf[25];

    int ret,addrlen = sizeof(struct sockaddr_in),clfd; 
    struct sockaddr_in client;

    bzero(&client,sizeof(client));

//accept   
    printf("accepting\n");
    clfd = accept(sockfd,(struct sockaddr *)&client,&addrlen);

//recv
    printf("accepted\n");
    bzero(buf,sizeof(buf));
    recv(clfd,buf,20,0);
    printf("recived\n");

//calculate
    a = buf[0] - '0';
    b = buf[1] - '0';
    op = buf[2];

    switch(op)
    {
        case '+':ret = a + b;break;
        case '-':ret = a - b;break;
        case '*':ret = a * b;break;
        case '/':ret = a / b;break;
    }// switch

    sprintf(bufret,"the result:%d",ret);

//send
    printf("sending\n");
    if(send(clfd,bufret,20,0) < 0)
    {
        printf("server send error\n");
        return -1;
    }// if
    printf("sended,server end\n");
    return 0;
}

int main(int argc,char * argv[])
{
    int sockfd;
    char addr[20];

    bzero(addr,sizeof(addr));
    sprintf(addr,"127.0.0.1");

    struct sockaddr_in server;
    bzero(&server,sizeof(server));
    server.sin_family = AF_INET;
    server.sin_port = htons(6000);
    //server.sin_addr.s_addr = htonl(INADDR_ANY);
    inet_pton(AF_INET,addr,(void *)&server.sin_addr);

    if((sockfd = initserver(SOCK_STREAM,(struct sockaddr *)&server,sizeof(server),1)) < 0)
    {
        printf("initserver error\n");
        return 0;
    }// if

//prepare server
    while(1)
    {
        pid_t pid;
        if(pid = fork() < 0)    //  fork error
        {
            close(sockfd);
            return -1;
        }
        else if(pid == 0)
        {
            printf("serving\n");
            serve(sockfd);
            break;
        }// if
    }// while

//serve
    close(sockfd);
    return 0;
}

test.sh

#!/bin/bash

./client1 1 2 +
./client2 2 3 +
./client3 3 4 +

本文完 2012-08-06

Dylan http://daoluan.github.io/blog/

06 August 2012 会持续更新