Linux网络编程基础＜多进程并发服务器＞

一、应用场景

• 最简单的socket示列代码只能一个客户端连接一个服务器，并不支持多个客户端对服务器的连接，为了能让多个客户端进行连接所以需要多进程或者多线程处理

二、思路解析

服务器端的程序是俩个套接字socket创建一个lfd，accept创建一个cfd阻塞连接套接字

所以只需要在fork创建的子线程里面处理与客户端的数据通信，在父进程处理连接客户端的数量处理，也就是回收进程资源。

Socket();		//创建监听套接字lfd
Bind();			//绑定服务器地址结构
Listen();		//设置监听上限
while(1){
	cfd=Accept();
	pid=fork();
	if(pid==0){
		close(lfd);		//子进程用不到lfd
		read(cfd);
		数据处理;
		write(cfd);
	}else if(pid>0){
		close(cfd);		//父进程用不到cfd
	}
}
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总结:

子进程:c

1. close(lfd);
2. read();
3. 数据处理;
4. wirte();

父进程:

• 注册信号捕捉函数:SIGNAL;
• 在回调函数中完成子进程回收:while(waitpid());

三、示列demo

重要API

• socket套接字
  socket、bind、listen、accept、connect

• 文件API
  open、read、write、close

• 进程API
  sigaction waitpid waitppid

多进程并发服务器未带回收进程处理

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


#define SERIVER_PORT 9999

int main(void)
{

    pid_t pid;
    int lfd, cfd;
    int ret, i;
    struct sockaddr_in myseriver;
    struct sockaddr_in myclient;
    int myclient_len = 0;
    char buf[100] = {0};

    lfd = socket(AF_INET, SOCK_STREAM, 0);
    if (lfd < 0)
    {
        perror("socket is error");
        exit(1);
    }

    myseriver.sin_family = AF_INET;
    myseriver.sin_port = htons(SERIVER_PORT);
    myseriver.sin_addr.s_addr = htonl(INADDR_ANY);

    ret = bind(lfd, (struct sockaddr *)&myseriver, sizeof(myseriver));
    if (ret < 0)
    {
        perror("bind is error");
        exit(1);
    }

    ret = listen(lfd, 128);
    if (ret < 0)
    {
        perror("listen is error");
        exit(1);
    }

    myclient_len = sizeof(myclient);
    while (1)
    {
        cfd = accept(lfd, (struct sockaddr *)&myclient, &myclient_len);
        if (cfd < 0)
        {
            perror("accept is error");
            exit(1);
        }

        pid = fork();
        if (pid == 0)
        {
            close(lfd);
            printf("childinit is success");

            while (1)
            {
                ret = read(cfd, buf, sizeof(buf));
                if (ret == 0)
                {
                    close(cfd);
                    exit(1);
                }

                for (i = 0; i < ret; i++)
                    buf[i] = toupper(buf[i]);
                write(cfd, buf, ret);
                write(STDOUT_FILENO, buf, ret);
            }
        }
        else if (pid < 0)
        {
            perror("fork is error");
            exit(1);
        }
        else
        {
           close(cfd);
        }
    }
}
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多进程并发服务器带回收进程处理

#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 


#define SERIVER_PORT 9999

void back_child(int signum)
{
    while((waitpid(0,NULL,WNOHANG))>0);
    return;
}

int main(void)
{

    pid_t pid;
    int lfd, cfd;
    int ret, i;
    struct sockaddr_in myseriver;
    struct sockaddr_in myclient;
    int myclient_len = 0;
    char buf[100] = {0};

    lfd = socket(AF_INET, SOCK_STREAM, 0);
    if (lfd < 0)
    {
        perror("socket is error");
        exit(1);
    }

    myseriver.sin_family = AF_INET;
    myseriver.sin_port = htons(SERIVER_PORT);
    myseriver.sin_addr.s_addr = htonl(INADDR_ANY);

    ret = bind(lfd, (struct sockaddr *)&myseriver, sizeof(myseriver));
    if (ret < 0)
    {
        perror("bind is error");
        exit(1);
    }

    ret = listen(lfd, 128);
    if (ret < 0)
    {
        perror("listen is error");
        exit(1);
    }

    myclient_len = sizeof(myclient);
    while (1)
    {
        cfd = accept(lfd, (struct sockaddr *)&myclient, &myclient_len);
        if (cfd < 0)
        {
            perror("accept is error");
            exit(1);
        }

        pid = fork();
        if (pid == 0)
        {
            close(lfd);
            printf("childinit is success");

            while (1)
            {
                ret = read(cfd, buf, sizeof(buf));
                if (ret == 0)
                {
                    close(cfd);
                    exit(1);
                }

                for (i = 0; i < ret; i++)
                    buf[i] = toupper(buf[i]);
                write(cfd, buf, ret);
                write(STDOUT_FILENO, buf, ret);
            }
        }
        else if (pid < 0)
        {
            perror("fork is error");
            exit(1);
        }
        else
        {
            struct sigaction act;
            act.sa_handler = back_child;
            sigemptyset(&act.sa_mask); 
            act.sa_flags = 0;
            ret = sigaction(SIGHUP, &act, NULL);
            if (ret != 0)
            {
                perror("signal is error");
            }

            close(cfd);
        }
    }
}
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四、效果展示