多进程并发服务器

使用多进程并发服务器时要考虑以下几点：

1. 父进程最大文件描述个数(父进程中需要close关闭accept返回的新文件描述符)
2. 系统内创建进程个数(与内存大小相关)
3. 进程创建过多是否降低整体服务性能(进程调度)

/* wrap.h */
#ifndef __WRAP_H_
#define __WRAP_H_

void perr_exit(const char *s);
int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr);
int Bind(int fd, const struct sockaddr *sa, socklen_t salen);
int Connect(int fd, const struct sockaddr *sa, socklen_t salen);
int Listen(int fd, int backlog);
int Socket(int family, int type, int protocol);
ssize_t Read(int fd, void *ptr, size_t nbytes);
ssize_t Write(int fd, const void *ptr, size_t nbytes);
int Close(int fd);
ssize_t Readn(int fd, void *vptr, size_t n);
ssize_t Writen(int fd, const void *vptr, size_t n);
ssize_t my_read(int fd, char *ptr);
ssize_t Readline(int fd, void *vptr, size_t maxlen);

#endif

/* wrap.c */
#include 
#include 
#include 
#include 
#include 

void perr_exit(const char *s)
{
	perror(s);
	exit(-1);
}

int Accept(int fd, struct sockaddr *sa, socklen_t *salenptr)
{
	int n;

again:
	if ((n = accept(fd, sa, salenptr)) < 0) {
		if ((errno == ECONNABORTED) || (errno == EINTR))
			goto again;
		else
			perr_exit("accept error");
	}
	return n;
}

int Bind(int fd, const struct sockaddr *sa, socklen_t salen)
{
    int n;

	if ((n = bind(fd, sa, salen)) < 0)
		perr_exit("bind error");

    return n;
}

int Connect(int fd, const struct sockaddr *sa, socklen_t salen)
{
    int n;

	if ((n = connect(fd, sa, salen)) < 0)
		perr_exit("connect error");

    return n;
}

int Listen(int fd, int backlog)
{
    int n;

	if ((n = listen(fd, backlog)) < 0)
		perr_exit("listen error");

    return n;
}

int Socket(int family, int type, int protocol)
{
	int n;

	if ((n = socket(family, type, protocol)) < 0)
		perr_exit("socket error");

	return n;
}

ssize_t Read(int fd, void *ptr, size_t nbytes)
{
	ssize_t n;

again:
	if ( (n = read(fd, ptr, nbytes)) == -1) {
		if (errno == EINTR)
			goto again;
		else
			return -1;
	}
	return n;
}

ssize_t Write(int fd, const void *ptr, size_t nbytes)
{
	ssize_t n;

again:
	if ( (n = write(fd, ptr, nbytes)) == -1) {
		if (errno == EINTR)
			goto again;
		else
			return -1;
	}
	return n;
}

int Close(int fd)
{
    int n;
	if ((n = close(fd)) == -1)
		perr_exit("close error");

    return n;
}

/*参三: 应该读取的字节数*/
ssize_t Readn(int fd, void *vptr, size_t n)
{
	size_t  nleft;              //usigned int 剩余未读取的字节数
	ssize_t nread;              //int 实际读到的字节数
	char   *ptr;

	ptr = vptr;
	nleft = n;

	while (nleft > 0) {
		if ((nread = read(fd, ptr, nleft)) < 0) {
			if (errno == EINTR)
				nread = 0;
			else
				return -1;
		} else if (nread == 0)
			break;

		nleft -= nread;
		ptr += nread;
	}
	return n - nleft;
}

ssize_t Writen(int fd, const void *vptr, size_t n)
{
	size_t nleft;
	ssize_t nwritten;
	const char *ptr;

	ptr = vptr;
	nleft = n;
	while (nleft > 0) {
		if ( (nwritten = write(fd, ptr, nleft)) <= 0) {
			if (nwritten < 0 && errno == EINTR)
				nwritten = 0;
			else
				return -1;
		}

		nleft -= nwritten;
		ptr += nwritten;
	}
	return n;
}

static ssize_t my_read(int fd, char *ptr)
{
	static int read_cnt;
	static char *read_ptr;
	static char read_buf[100];

	if (read_cnt <= 0) {
again:
		if ( (read_cnt = read(fd, read_buf, sizeof(read_buf))) < 0) {
			if (errno == EINTR)
				goto again;
			return -1;
		} else if (read_cnt == 0)
			return 0;
		read_ptr = read_buf;
	}
	read_cnt--;
	*ptr = *read_ptr++;

	return 1;
}

ssize_t Readline(int fd, void *vptr, size_t maxlen)
{
	ssize_t n, rc;
	char    c, *ptr;

	ptr = vptr;
	for (n = 1; n < maxlen; n++) {
		if ( (rc = my_read(fd, &c)) == 1) {
			*ptr++ = c;
			if (c  == '\n')
				break;
		} else if (rc == 0) {
			*ptr = 0;
			return n - 1;
		} else
			return -1;
	}
	*ptr  = 0;

	return n;
}

/* server.c */
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 
#include 

#include "wrap.h"

#define SRV_PORT 9999

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

int main(int argc, char *argv[])
{
    pid_t pid;
    int ret;

    int i; //循环因子 i
    char buf[BUFSIZ]; // 子进程buf

    int lfd, cfd;

    struct sockaddr_in srv_addr; //定义服务器地址结构

    struct sockaddr_in clt_addr; // 4 定义客户端地址结构
    socklen_t clt_addr_len; // 4
    
    //memset(&srv_addr, 0, sizeof(srv_addr)); //将地址结构清零
    bzero(&srv_addr, sizeof(srv_addr));

    srv_addr.sin_family = AF_INET; //初始化 IPv4
    srv_addr.sin_port = htons(SRV_PORT); //端口号 转为网络字节序
    srv_addr.sin_addr.s_addr = htonl(INADDR_ANY); //获取本机任意有效IP

    lfd = Socket(AF_INET, SOCK_STREAM, 0); // 1 创建套接字，返回一个文件描述符

    Bind(lfd, (struct sockaddr *)&srv_addr, sizeof(srv_addr));// 2 将文件描述符与本地IP端口进行绑定

    Listen(lfd, 128); // 3 监听

    clt_addr_len = sizeof(clt_addr); // 4

    while(1){ //可自定义条件
        cfd = Accept(lfd, (struct sockaddr *)&clt_addr, &clt_addr_len); // 4 阻塞等待客户端连接请求

        pid = fork();
        if(pid < 0){
            perr_exit("fork error"); //封装在wrap.c中
        }else if(pid == 0){
            break;
        }else{
            struct sigaction act;

            act.sa_handler = catch_child;
            sigemptyset(&act.sa_mask);
            act.sa_flags = 0;
            
            ret = sigaction(SIGCHLD, &act, NULL);
            if(ret != 0){
                perr_exit("sigaction error");
            }
            close(cfd);
            continue;
        }
    }

    if(pid == 0){ //子进程
        for(;;){
            ret = Read(cfd, buf, sizeof(buf));
            if(ret == 0 ){ //检测到客户端关闭
                close(cfd);
                exit(1); //异常终止退出
            }

            for(i = 0; i < ret; i++){
                buf[i] = toupper(buf[i]); //小写 ——> 大写
            }

            write(cfd, buf, ret); //写到buf
            write(STDOUT_FILENO, buf, ret); //写到屏幕以便查看
        }
    }
    return 0;
}