简单的TCP并发服务器程序学习

tcpserv.c

#include "head.h"


int
main(int argc, char **argv)
{
   int listenfd, connfd;
   pid_t                        childpid;
   socklen_t                    clilen;
   struct sockaddr_in   cliaddr, servaddr;


   listenfd = socket(AF_INET, SOCK_STREAM, 0);


   bzero(&servaddr, sizeof(servaddr));
   servaddr.sin_family = AF_INET;
   servaddr.sin_addr.s_addr = htonl(INADDR_ANY); //host to network long
   servaddr.sin_port = htons(SERV_PORT);//host to network short


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


   listen(listenfd, BACKLOG);


   for (;;) {
      clilen = sizeof(cliaddr);
     connfd = accept(listenfd, (struct sockaddr *)&cliaddr, &clilen);
      if ((childpid = fork()) == 0){//child process
         close(listenfd);//close listening socket
         str_echo(connfd);//process the request
         exit(0);
      }
      close(connfd);//parent closes connected socket
   }
}

str_echo.c

#include "head.h"

void
str_echo(int sockfd)
{
   ssize_t      n;
   char         buf[MAXLINE];

again:
   while ((n = read(sockfd, buf, MAXLINE)) > 0)
      write(sockfd, buf, n);
   if (n < 0 && errno == EINTR)//Interrupted fuunction call;
      goto again;
   else if (n < 0) //read error
      err_sys("str_echo:read error");
}

tcpcli.c

#include "head.h"

int
main(int argc, char **argv)
{
   int sockfd;
   struct sockaddr_in   servaddr;

   if (argc != 2)
      err_quit("usage: tcpcli");

   sockfd = socket(AF_INET, SOCK_STREAM, 0);

   bzero(&servaddr, sizeof(servaddr));
   servaddr.sin_family = AF_INET;
   servaddr.sin_port= ntohs(SERV_PORT);
   //presentation to numeric
   inet_pton(AF_INET, argv[1], &servaddr.sin_addr);

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

   str_cli(stdin, sockfd);

   exit(0);
}

str_cli.c

#include "head.h"

void
str_cli(FILE *fp, int sockfd)
{
   char         sendline[MAXLINE], recvline[MAXLINE];

   while (fgets(sendline, MAXLINE, fp) != NULL){
      write(sockfd, sendline, strlen(sendline));
      if (Readline(sockfd, recvline, MAXLINE) == 0)
         err_quit("str_cli: server terminated prematurely");
      fputs(recvline, stdout);
   }
}

Readline.c

#include "head.h"

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++) {
      again:
         if ((rc = read(fd, &c, 1)) == 1){
            *ptr++ = c;
            if (c == '\n')
               break;
         } else if (rc == 0) {
            *ptr = 0;
            return (n - 1);
         } else {
            if (errno == EINTR)
               goto again;
            return (-1);
         }
   }

   *ptr = 0;
   return (n);
}

head.h

#include <netinet/in.h>
#include <unistd.h>
#include <sys/socket.h>
#include <errno.h>
#include <stdio.h>
#include <strings.h>
#include <string.h>
//#include <stdlib.h>

#define         SERV_PORT       9877
#define         BACKLOG         5
#define         MAXLINE         2048

error.c

#include "head.h"
#include <stdarg.h>
#include <syslog.h>

int daemon_proc;

static void err_doit(int, int, const char *, va_list);
void
err_sys(const char *fmt, ...)
{
   va_list ap;

   va_start(ap, fmt);
   err_doit(1, LOG_ERR, fmt, ap);
   va_end(ap);
   exit(1);
}

void
err_dump(const char *fmt, ...)
{
   va_list      ap;

   va_start(ap, fmt);
   err_doit(1, LOG_ERR, fmt, ap);
   va_end(ap);
   abort();
   exit(1);
}
void
err_msg(const char *fmt, ...)
{
   va_list      ap;

   va_start(ap, fmt);
   err_doit(0, LOG_INFO, fmt, ap);
   va_end(ap);
   return;
}

void
err_quit(const char *fmt, ...)
{
   va_list      ap;

   va_start(ap, fmt);
   err_doit(0, LOG_ERR, fmt, ap);
   va_end(ap);
   exit(1);
}

static void
err_doit(int errnoflag, int level, const char *fmt, va_list ap)
{
   int errno_save, n;
   char         buf[MAXLINE + 1];

   errno_save = errno;
#ifdef  HAVE_VSNPRINTF
   vsnprintf(buf, MAXLINE, fmt, ap);
#else
   vsprintf(buf, fmt, ap);
#endif
   n = strlen(buf);
   if (errnoflag)
      snprintf(buf + n, MAXLINE - n, ": %s", strerror(errno_save));
   strcat(buf, "\n");

   if (daemon_proc){
      syslog(level, buf);
   } else {
      fflush(stdout);
      fputs(buf, stderr);
      fflush(stderr);
   }
   return;
}