I wrote a simple socket program in C, but met an question:my server program cann't receive data from the client program, though the client program can receive data from the server program. Why? I went back to many books and many webpages of the Internet, but cann't find the reason.
Who can tell me the reason,thanks
Below is the program.

/******* server.c ************/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
#include <arpa/inet.h>

int main(int argc, char *argv[])
{
int sockfd,new_fd;
struct sockaddr_in server_addr;
struct sockaddr_in client_addr;
int sin_size,portnumber, recv_len;
char buffer[1024];

if(argc!=2)
{
fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]);
exit(1);
}

if((portnumber=atoi(argv[1]))<0)
{
fprintf(stderr,"Usage:%s portnumber\a\n",argv[0]);
exit(1);
}

/* build socke */
if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
{
fprintf(stderr,"Socket error:%s\n\a",strerror(errno));
exit(1);
}

/* fill sockaddr struct */
bzero(&server_addr,sizeof(struct sockaddr_in));
server_addr.sin_family=AF_INET;
server_addr.sin_addr.s_addr=htonl(INADDR_ANY);
server_addr.sin_port=htons(portnumber);

/* bind sockfd */
if(bind(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr))== -1)
{
fprintf(stderr,"Bind error:%s\n\a",strerror(errno));
exit(1);
}

/*listen socket */
if(listen(sockfd,5)==-1)
{
fprintf(stderr,"Listen error:%s\n\a",strerror(errno));
exit(1);
}
while(1)
{
/*wait for connect*/
sin_size=sizeof(struct sockaddr_in);
if((new_fd=accept(sockfd,(struct sockaddr *)(&client_addr),(socklen_t *)&sin_size ))==-1)
{
fprintf(stderr,"Accept error:%s\n\a",strerror(errno));
exit(1);
}
fprintf(stderr,"Server get connection from %s\n",inet_ntoa(client_addr.sin_addr));

recv_len = -1;
while(recv_len == -1)
{
recv_len=recv(sockfd,buffer,1024, 0);
if(recv_len != -1)
{
buffer[recv_len]='\0';
printf("received:%s\n",buffer);
}
}
/* the communication is end */
shutdown(new_fd, SHUT_RD);
/* for the next */
}
shutdown(sockfd, SHUT_RD);
exit(0);
}

Can you use the code tag ? Indentation would ease reading your program.

/******* client.c ************/
#include <stdlib.h>
#include <stdio.h>
#include <errno.h>
#include <string.h>
#include <netdb.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <sys/socket.h>
int main(int argc, char *argv[])
{
int sockfd;
char hello[]="I'm ljqu_happy.\n";
char buffer[1024];
struct sockaddr_in server_addr;
struct hostent *host;
int portnumber,nbytes, recv_len;

if(argc!=3)
{
fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
exit(1);
}

if((host=gethostbyname(argv[1]))==NULL)
{
fprintf(stderr,"Gethostname error\n");
exit(1);
}

if((portnumber=atoi(argv[2]))<0)
{
fprintf(stderr,"Usage:%s hostname portnumber\a\n",argv[0]);
exit(1);
}

/* build socket */
if((sockfd=socket(AF_INET,SOCK_STREAM,0))==-1)
{
fprintf(stderr,"Socket Error:%s\a\n",strerror(errno));
exit(1);
}

/* fill socket */
bzero(&server_addr,sizeof(server_addr));
server_addr.sin_family=AF_INET;
server_addr.sin_port=htons(portnumber);
server_addr.sin_addr=*((struct in_addr *)host->h_addr);

/* connect to server */
if(connect(sockfd,(struct sockaddr *)(&server_addr),sizeof(struct sockaddr)
)==-1)
{
fprintf(stderr,"Connect Error:%s\a\n",strerror(errno));
exit(1);
}

/* connect successful */
if((send(sockfd, hello, sizeof(hello), 0))==-1)
{
fprintf(stderr,"send name Error:%s\n",strerror(errno));
exit(1);
}
printf("send data %s OK!\n", hello);

/*communication is end */
shutdown(sockfd, SHUT_RD);
exit(0);
}

No improvement in your code readability, but anyway you use the wrong file descriptor in your recv call, it should be new_fd.

why this forum doesn't have file attachment function?
Is there special reason about it?

--

Jlliagre is wellcome You gave the right answer.Thank you very much.But I'm very sorry for asking such a simple question,I thought things too complicated, and didn't just sit down to look carefully at my code.I should remember this lesson.
BTW, I have indented the code, but the web don't support the space at the head of the line, there only left space line.

As I asked you before, put your code between code tags, like this