回射客户端服务器中僵尸进程的处理( the solution of zombie process in the echo client && server )

Tips :

In the passage , we discuss how to clean up zombie processes with a better solution. We attempted signal ( SIGCHLD , SIG_IGN ), but it can't manage many son processes. The same things happened to wait. Finally we use waitpid() to solve this problem to manage
a number of zombie processes that may happen in the programming.

Server :

/***********************************************************************
> filename: echoserv2.c
> Author: ma6174
> Mail: ma6174@163.com
> Created Time: Thu 29 Oct 16:38:57 2015
************************************************************************/

#include <signal.h>
#include <stdio.h>
#include <sys/socket.h>
#include <string.h>
#include <arpa/inet.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <sys/wait.h>
#define ERR_EXIT(m) \
do \
{\
perror(m) ;\
exit(EXIT_FAILURE) ;\
}while(0)

//ssize_t the signed integer , size_t the unsigned integer
ssize_t readn ( int fd , void *buf , size_t count )   //encapsulate like read function
{
size_t nleft = count ;
ssize_t nread ;
char *bufp ;
bufp = ( char *) buf ;
while ( nleft > 0 )
{
//nread = read ( fd , bufp , nleft ) ;
//printf ("nread = %d\n" , nread ) ;
if ( (nread = read ( fd , bufp , nleft )) < 0  )
{
if ( EINTR  == errno ) // interrupted by the signal , we don't think this occasion is a mistake
{
continue ;
}
return -1 ;  		//failure
}
else if ( 0 == nread )  // peer close
{
return count - nleft ;
}
bufp += nread ;
nleft -= nread ;
}
return count ;
}

ssize_t writen ( int fd ,const void *buf , size_t count )
{
size_t nleft = count ;
ssize_t nwritten ;
char * bufp ;
bufp = (char*) buf ;
while ( nleft > 0 )
{
if ( ( nwritten = write ( fd , bufp , nleft ) ) < 0 )
{
if ( EINTR == errno )
{
continue ;
}
return -1 ;
}
else if ( 0 == nwritten )    // like nothing happened to write function
{
continue ;
}
bufp += nwritten ;
nleft -= nwritten ;
}
return count ;
}

ssize_t recv_peek ( int sockfd , void *buf , size_t len )
{
while ( 1 )
{
int ret = recv ( sockfd , buf , len , MSG_PEEK ) ;
//only let buf read the data from sockfd but not remove the data from that sockfd(socket)
//in comparison with read function it receive the data and remove the data in the socket
if ( -1 == ret && EINTR == errno )
{
continue ;			//interrupted by signal
}
return ret ;
}
}

ssize_t readline ( int sockfd , void *buf  , size_t maxline )
{
int ret ;
int nread ;
char *bufp ;
bufp = (char*) buf ;
int nleft ;
nleft = maxline ;
while (1 )
{
ret = recv_peek ( sockfd, bufp , nleft ) ;
if ( ret < 0 )    //failure
{
return ret ;
}
else if ( 0 == ret )		// peer closed
{
return ret ;
}
nread = ret ;
int i ;
for ( i = 0 ; i < nread ; i ++ )
{
if ( '\n' ==  bufp[i])
{
ret = readn (sockfd,bufp , i+1) ;
if ( ret != i + 1 )
{
exit(EXIT_FAILURE) ;
}
return ret ;
}
}
if ( nread > nleft )   // the data that we read(nread) can't be more than the real data in the socket
{
exit ( EXIT_FAILURE ) ;
}
nleft -= nread ;
ret = readn ( sockfd , bufp , nread ) ;  // read n characters from the socket ( don't contain '\n')
if ( ret != nread )
{
exit(EXIT_FAILURE ) ;
}
bufp += nread ;
}
return -1 ;
}

void echo_serv ( int conn )
{
char recvbuf[1024] ;
while(1)
{
memset ( recvbuf , 0 , sizeof(recvbuf) ) ;
int ret = readline ( conn , recvbuf , sizeof(recvbuf) ) ;
if ( -1 == ret )
{
ERR_EXIT("readline") ;
}
if ( 0 == ret )
{
//	ERR_EXIT ("client close\n") ;
printf("client close\n") ;
break ;
}
fputs ( recvbuf , stdout ) ;
writen ( conn , recvbuf , strlen(recvbuf) ) ;
}
}

void handle_sigchld ( int sig )
{
//	wait ( NULL ) ; 	//call wait function to catch the process of the son
/*ther will be a problem to call wait if there many sons' processes , wait function can
not wait all the sons' processes to quit. Another saying is that wait funciton can not
guarantee that there is clear of zombie processes when many sons's processes exist.
wait function only wait for the first son process to quit ,then wait will quit immediately.
In order to improve this performance , we use waitpid() to change.
*/
//	static i = 0 ;
//	printf ("i = %d\n",++i ) ;

while ( waitpid(-1,NULL,WNOHANG) > 0 )
;
/*-1 means all of the son process will quit,WNOHANG means wait no hang
no hang means when there is no son process , waitpid will return -1 :*/
}
int
main ()
{

signal ( SIGCHLD , handle_sigchld ) ;
//	signal ( SIGCHLD , SIG_IGN ) ;
/* neglect the signal of SIGCHLD to avoid zombie process which happened to
the server when the client quit , but the server still keeps listening.*/
int listenfd ;
if (( listenfd = socket ( PF_INET , SOCK_STREAM , IPPROTO_TCP )) < 0 )
{
ERR_EXIT("socket") ;
}
struct sockaddr_in servaddr ;
memset ( & servaddr , 0 , sizeof(servaddr ) ) ;
servaddr.sin_family = AF_INET ;
servaddr.sin_port = htons (5188) ;
servaddr.sin_addr.s_addr  = htonl(INADDR_ANY) ;		//INTADDR_ANY == 0

//other two means to change the host address to network address
//servaddr.sin_addr.s_addr = inet_addr("127.0.0.1") ;
//inet_aton("127.0.0.1" , &servaddr.sin_addr) ;

//set out the bind has already used by SO_REUSEADDR
int on = 1 ;
int opt ;
if (( opt = setsockopt (listenfd ,SOL_SOCKET , SO_REUSEADDR, &on , sizeof(on) )) < 0 )
{
ERR_EXIT("setsocketopt") ;
}
if ( bind ( listenfd , (struct sockaddr * ) &servaddr  , sizeof(servaddr )) < 0 )
{
ERR_EXIT("bind") ;
}
if ( listen ( listenfd , SOMAXCONN) < 0 )
{
ERR_EXIT("listen") ;
}
struct sockaddr_in peeraddr ;
socklen_t peerlen = sizeof(peeraddr) ;
int conn ;
while ( 1 )
{
if ( (conn = accept ( listenfd , ( struct sockaddr * )&peeraddr , &peerlen )) < 0 )
{
ERR_EXIT("accept") ;
}

// print the client's address and ip '
printf ("ip = %s port = %d\n", inet_ntoa(peeraddr.sin_addr) ,ntohs(peeraddr.sin_port) )  ;
int pid ;
pid = fork()  ;  // creat the child process to set out the multi-connection from clients
if ( -1 == pid )
{
ERR_EXIT ("fork") ;
}
if ( 0 == pid )
{
close (listenfd) ; // the son's pid didn't need to process the listen , so we close listenfd ;
echo_serv (conn) ;
exit(EXIT_SUCCESS) ;
}
else
{
close (conn) ;    // the father's pid didn't need  to process the acceept ,so we close conn '
}
}
return 0 ;
}

Client :

/************************************************************************
> filename : echocli.c
> Author: ma6174
> Mail: ma6174@163.com
> Created Time: Thu 29 Oct 16:38:57 2015
************************************************************************/

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

#define ERR_EXIT(m) \
do \
{\
perror(m) ;\
exit(EXIT_FAILURE) ;\
}while(0)

//ssize_t signed integer   size_t unsigned integer
ssize_t readn ( int fd , void *buf , size_t count )    // encapsulate readn as the function of read
{
size_t nleft = count ;
ssize_t nread ;
char *bufp ;
bufp = ( char *) buf ;
//	printf ("nleft = %d\n" , nleft ) ;
while ( nleft > 0 )
{
//		printf ("nleft = %d\n" , nleft ) ;
nread = read ( fd , bufp , nleft ) ;
//                printf ("nread = %d\n" , nread ) ;
if( nread  < 0 )
{
if ( errno == EINTR )   // interrupted by signal , we don't think this occasion is not right
{
continue ;
}
return -1 ;
}
else if ( 0 == nread )    //peer closed
{
return count - nleft ;
//break ;
}
//		printf ("nreaad = %d\n" , nread ) ;
bufp += nread ;
nleft -= nread ;
}
return  count ;
}

ssize_t writen ( int fd , const void *buf ,size_t count )
{
size_t nleft = count ;
ssize_t nwritten ;
char *bufp ;
bufp = ( char * ) buf ;
while ( nleft > 0 )
{
if ( ( nwritten = write ( fd , bufp , nleft ) ) < 0 )
{
if ( errno == EINTR )  // just like the occasion in writen
{
continue ;
}
return -1 ;
}
else if ( 0 == nwritten  ) // if 0 == nread , like nothing happened to write ...
{
continue ;
}
bufp += nwritten ;
nleft -= nwritten ;
}
return count ;
}

ssize_t recv_peek ( int sockfd , void *buf , size_t len )
{
while ( 1 )
{
int ret = recv ( sockfd , buf , len , MSG_PEEK ) ;
//only let buf read the data from sockfd but not remove the data from that sockfd(socket)
//in comparison with read function it receive the data and remove the data in the socket
if ( -1 == ret && EINTR == errno )
{
continue ;			//interrupted by signal
}
return ret ;
}
}

ssize_t readline ( int sockfd , void *buf  , size_t maxline )
{
int ret ;
int nread ;
char *bufp ;
bufp = (char*) buf ;
int nleft ;
nleft = maxline ;
while (1 )
{
ret = recv_peek ( sockfd, bufp , nleft ) ;
if ( ret < 0 )    //failure
{
return ret ;
}
else if ( 0 == ret )		// peer closed
{
return ret ;
}
nread = ret ;
int i ;
for ( i = 0 ; i < nread ; i ++ )
{
if ( '\n' ==  bufp[i])
{
ret = readn (sockfd,bufp , i+1) ;
if ( ret != i + 1 )
{
exit(EXIT_FAILURE) ;
}
return ret ;
}
}
if ( nread > nleft )   // the data that we read(nread) can't be more than the real data in the socket
{
exit ( EXIT_FAILURE ) ;
}
nleft -= nread ;
ret = readn ( sockfd , bufp , nread ) ;  // read n characters from the socket ( don't contain '\n')
if ( ret != nread )
{
exit(EXIT_FAILURE ) ;
}
bufp += nread ;
}
return -1 ;
}

void echo_cli ( int sock )
{
char sendbuf[1024]={0} ;
char recvbuf[1024]={0} ;
memset ( sendbuf , 0 , sizeof(sendbuf) ) ;
memset ( recvbuf , 0 , sizeof(recvbuf) ) ;
int n ;
while( fgets ( sendbuf , sizeof(sendbuf) , stdin ) != NULL )
{
//fgets get the data with '\n' in default
writen ( sock , sendbuf ,strlen(sendbuf) ) ;     // the former 4 bytes and  the real data(n)
int ret = readline ( sock , recvbuf , sizeof(recvbuf) ) ;
if ( -1 == ret )
{
ERR_EXIT ("readline") ;
}
else if ( 0 == ret  )            //may interrupted by signal
{
printf ("clien________ close\n") ;
break ;
}
fputs ( recvbuf , stdout ) ;
memset ( sendbuf , 0 , sizeof(sendbuf) ) ;
memset ( recvbuf , 0 , sizeof(recvbuf) ) ;
}
close ( sock ) ;
}

int
main ()
{
int sock[5] ;     //create multi-connection to the server
int i ;
for ( i = 0 ; i < 5 ; i ++ )
{

if (( sock[i]= socket ( PF_INET , SOCK_STREAM , IPPROTO_TCP )) < 0 )
{
ERR_EXIT("socket") ;
}
struct sockaddr_in servaddr ;
memset ( & servaddr , 0 , sizeof(servaddr) ) ;
servaddr.sin_family = AF_INET ;
servaddr.sin_port = htons (5188) ;
//servaddr.sin_addr.s_addr  = htonl(INADDR_ANY) ;
servaddr.sin_addr.s_addr = inet_addr("127.0.0.1") ;
//inet_aton("127.0.0.1" , &servaddr.sin_addr) ;
if ( connect ( sock[i] , ( struct sockaddr * )& servaddr, sizeof(servaddr )) < 0 )
{
ERR_EXIT("connet") ;
}
}
echo_cli(sock[0]) ;
return 0 ;
}