实现迭代型的echo服务器

代码仓库地址

Socket服务器设计

​ 对于使用socket的网络服务器端程序，有两种常见的设计方式：

1. 迭代式：服务器每次只处理一个客户端，只有当完全处理完一个客户端的请求后才会去处理下一个客户端
2. 并发型：能够同时处理单个客户端的请求

实现迭代型的echo服务器

#include <syslog.h>
#include <sys/stat.h>
#include <fcntl.h>
#include "sys_tem.h"

//< 创建迭代型 echo 服务器

#define BD_NO_CHDIR           01    /* Don't chdir("/") */
#define BD_NO_CLOSE_FILES     02    /* Don't close all open files */
#define BD_NO_REOPEN_STD_FDS  04    /* Don't reopen stdin, stdout, and
                                       stderr to /dev/null */
#define BD_NO_UMASK0         010    /* Don't do a umask(0) */

#define BD_MAX_CLOSE  8192          /* Maximum file descriptors to close if
                                       sysconf(_SC_OPEN_MAX) is indeterminate */
int becomeDaemon(int flags);
//< 调用会使一个程序变成守护进程
int becomeDaemon(int flags)
{
    int maxfd, fd;

    switch (fork()) {                   /* Become background process */
    case -1: return -1;
    case 0:  break;                     /* Child falls through... */
    default: _exit(EXIT_SUCCESS);       /* while parent terminates */
    }

    if (setsid() == -1)                 /* Become leader of new session */
        return -1;

    switch (fork()) {                   /* Ensure we are not session leader */
    case -1: return -1;
    case 0:  break;
    default: _exit(EXIT_SUCCESS);
    }

    if (!(flags & BD_NO_UMASK0))
        umask(0);                       /* Clear file mode creation mask */

    if (!(flags & BD_NO_CHDIR))
        chdir("/");                     /* Change to root directory */

    if (!(flags & BD_NO_CLOSE_FILES)) { /* Close all open files */
        maxfd = sysconf(_SC_OPEN_MAX);
        if (maxfd == -1)                /* Limit is indeterminate... */
            maxfd = BD_MAX_CLOSE;       /* so take a guess */

        for (fd = 0; fd < maxfd; fd++)
            close(fd);
    }

    if (!(flags & BD_NO_REOPEN_STD_FDS)) {
        close(STDIN_FILENO);            /* Reopen standard fd's to /dev/null */

        fd = open("/dev/null", O_RDWR);

        if (fd != STDIN_FILENO)         /* 'fd' should be 0 */
            return -1;
        if (dup2(STDIN_FILENO, STDOUT_FILENO) != STDOUT_FILENO)
            return -1;
        if (dup2(STDIN_FILENO, STDERR_FILENO) != STDERR_FILENO)
            return -1;
    }

    return 0;
}



#define SERVICE "echo"        

#define BUF_SIZE 500  
#define IS_ADDR_STR_LEN 4096          



int main(int argc, char *argv[])
{
    int sfd;
    ssize_t numRead;
    socklen_t len;
    struct sockaddr_storage claddr;
    char buf[BUF_SIZE];
    char addrStr[IS_ADDR_STR_LEN];
    //< 将该进程变成守护进程
    if (becomeDaemon(0) == -1)
        perror("becomeDaemon");

    //< 创建一个socket 成功返回 0 失败返回-1
    sfd = inetBind(SERVICE, SOCK_DGRAM, NULL);
    if (sfd == -1) {
        //< 创建socket失败，记录一下日志
        syslog(LOG_ERR, "Could not create server socket (%s)", strerror(errno));
        exit(EXIT_FAILURE);
    }

    /* Receive datagrams and return copies to senders */
    //< 收到之后，数收到的数据进行处理，并将原始数据回显的方式给发送者
    for (;;) {
        len = sizeof(struct sockaddr_storage);
        numRead = recvfrom(sfd, buf, BUF_SIZE, 0,
                           (struct sockaddr *) &claddr, &len);
        if (numRead == -1)
            perror("recvfrom");

        if (sendto(sfd, buf, numRead, 0, (struct sockaddr *) &claddr, len)
                        != numRead)
            syslog(LOG_WARNING, "Error echoing response to %s (%s)",
                    inetAddressStr((struct sockaddr *) &claddr, len,
                                   addrStr, IS_ADDR_STR_LEN),
                    strerror(errno));
    }
}