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1. 程序流程

多进程和多线程的服务器代码设计思路如下

2. 程序代码

2.1 多进程服务器

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

#include "wrap.h"

#define MAXLINE 8192
#define SERV_PORT 8000

void do_sigchild(int num)
{
    while (waitpid(0, NULL, WNOHANG) > 0)
        ;
}

int main(void)
{
    struct sockaddr_in servaddr, cliaddr;
    socklen_t cliaddr_len;
    int listenfd, connfd;
    char buf[MAXLINE];
    char str[INET_ADDRSTRLEN];
    int i, n;
    pid_t pid;
    struct sigaction newact;

    newact.sa_handler = do_sigchild;
    sigemptyset(&newact.sa_mask);
    newact.sa_flags = 0;
    sigaction(SIGCHLD, &newact, NULL);

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);

    int opt = 1;
    setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &opt, sizeof(opt));

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
    servaddr.sin_port = htons(SERV_PORT);

    Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

    Listen(listenfd, 20);

    printf("Accepting connections ...\n");
    while (1) {
        cliaddr_len = sizeof(cliaddr);
        connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);
        printf("-------------------------%d\n", connfd);

        pid = fork();
        if (pid == 0) {
            Close(listenfd);
            while (1) {
                n = Read(connfd, buf, MAXLINE);
                if (n == 0) {
                    printf("the other side has been closed.\n");
                    break;
                }
                printf("received from %s at PORT %d\n",
                        inet_ntop(AF_INET, &cliaddr.sin_addr, str, sizeof(str)),
                        ntohs(cliaddr.sin_port));

                for (i = 0; i < n; i++)
                    buf[i] = toupper(buf[i]);

                Write(STDOUT_FILENO, buf, n);
                Write(connfd, buf, n);
            }
            Close(connfd);
            return 0;
        } else if (pid > 0) {
            Close(connfd);
        }  else
            perr_exit("fork");
    }
    return 0;
}

2.2 多线程服务器

#include <stdio.h>
#include <string.h>
#include <arpa/inet.h>
#include <pthread.h>
#include <ctype.h>
#include <unistd.h>
#include <fcntl.h>

#include "wrap.h"

#define MAXLINE 8192
#define SERV_PORT 8000

struct s_info {                     //定义一个结构体, 将地址结构跟cfd捆绑
    struct sockaddr_in cliaddr;
    int connfd;
};

void *do_work(void *arg)
{
    int n,i;
    struct s_info *ts = (struct s_info*)arg;
    char buf[MAXLINE];
    char str[INET_ADDRSTRLEN];      //#define INET_ADDRSTRLEN 16  可用"[+d"查看

    while (1) {
        n = Read(ts->connfd, buf, MAXLINE);                     //读客户端
        if (n == 0) {
            printf("the client %d closed...\n", ts->connfd);
            break;                                              //跳出循环,关闭cfd
        }
        printf("received from %s at PORT %d\n",
                inet_ntop(AF_INET, &(*ts).cliaddr.sin_addr, str, sizeof(str)),
                ntohs((*ts).cliaddr.sin_port));                 //打印客户端信息(IP/PORT)

        for (i = 0; i < n; i++) 
            buf[i] = toupper(buf[i]);                           //小写-->大写

        Write(STDOUT_FILENO, buf, n);                           //写出至屏幕
        Write(ts->connfd, buf, n);                              //回写给客户端
    }
    Close(ts->connfd);

    return (void *)0;
}

int main(void)
{
    struct sockaddr_in servaddr, cliaddr;
    socklen_t cliaddr_len;
    int listenfd, connfd;
    pthread_t tid;

    struct s_info ts[256];      //创建结构体数组.
    int i = 0;

    listenfd = Socket(AF_INET, SOCK_STREAM, 0);                     //创建一个socket, 得到lfd

    bzero(&servaddr, sizeof(servaddr));                             //地址结构清零
    servaddr.sin_family = AF_INET;
    servaddr.sin_addr.s_addr = htonl(INADDR_ANY);                               //指定本地任意IP
    servaddr.sin_port = htons(SERV_PORT);                                       //指定端口号 

    Bind(listenfd, (struct sockaddr *)&servaddr, sizeof(servaddr));             //绑定

    Listen(listenfd, 128);                                                      //设置同一时刻链接服务器上限数

    printf("Accepting client connect ...\n");

    while (1) {
        cliaddr_len = sizeof(cliaddr);
        connfd = Accept(listenfd, (struct sockaddr *)&cliaddr, &cliaddr_len);   //阻塞监听客户端链接请求
        ts[i].cliaddr = cliaddr;
        ts[i].connfd = connfd;

        pthread_create(&tid, NULL, do_work, (void*)&ts[i]);
        pthread_detach(tid);                                                    //子线程分离,防止僵线程产生.
        i++;
    }

    return 0;
}

2.3 客户端测试程序

/* client.c */
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>

#include "wrap.h"

#define MAXLINE 8192
#define SERV_PORT 8000

int main(int argc, char *argv[])
{
    struct sockaddr_in servaddr;
    char buf[MAXLINE];
    int sockfd, n;

    sockfd = Socket(AF_INET, SOCK_STREAM, 0);

    bzero(&servaddr, sizeof(servaddr));
    servaddr.sin_family = AF_INET;
    inet_pton(AF_INET, "127.0.0.1", &servaddr.sin_addr);
    servaddr.sin_port = htons(SERV_PORT);

    Connect(sockfd, (struct sockaddr *)&servaddr, sizeof(servaddr));

    while (fgets(buf, MAXLINE, stdin) != NULL) {
        Write(sockfd, buf, strlen(buf));
        n = Read(sockfd, buf, MAXLINE);
        if (n == 0) {
            printf("the other side has been closed.\n");
            break;
        }
        else
            Write(STDOUT_FILENO, buf, n);
    }

    Close(sockfd);

    return 0;
}

2.4 错误处理函数封装

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 <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <errno.h>
#include <sys/socket.h>

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;
}

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