Why does this server not outputting anything? - c

Question

#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
int main()
{
int sock, newsock;
struct sockaddr server_name = {AF_UNIX, "Fred"};
socklen_t len=sizeof(struct sockaddr)+5;
if( (sock=socket(AF_UNIX,SOCK_STREAM,0)) ==-1)
{
printf("error creating socket");
return -1;
}
if( bind(sock,&server_name,len) != 0 ) //binding
{
printf("socket bind error ");
return -1;
}
if(listen(sock,10)!=0) //set sock to listen
{
printf("error listening");
return -1;
}
printf("Waiting for connections....");
while(1)
{
newsock=accept(sock, (struct sockaddr*)NULL, NULL);
char temp[1000]="gggggg\n";
write(newsock,temp,strlen(temp));
write(newsock,temp,strlen(temp));
close(newsock);
sleep(1);
}
return 0;
}
"Waiting for connections..." doesn't appear on my screen. What's the problem? I tried print function everywhere. Nothing shows up..What is the problem? I don't see that I closed stdout..Can anyone help? Thank you.

Answer 1

The standard output is line buffered by default. Your program outputs something without the new line and then enters the loop. You need to add a new line like this:
printf("Waiting for connections....\n");
For similar reasons, the error messages should be output to standard error, because it's not buffered.
fprintf(stderr, "error creating socket\n");

Answer 2

Firstly, you should add '\n' add the end of log:"Waiting for connections....\n", then the log cann't be buffered, and be outputted.
Secondly, your program is error, the correct program is like this:
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/un.h>
int main()
{
int sock, newsock;
struct sockaddr_un server_name;
socklen_t len= sizeof(server_name);
unlink("Fred");
if( (sock=socket(AF_UNIX,SOCK_STREAM,0)) ==-1)
{
printf("error creating socket\n");
return -1;
}
server_name.sun_family = AF_UNIX;
strcpy(server_name.sun_path, "Fred");
if( bind(sock,(struct sockaddr*)&server_name,len) != 0 ) //binding
{
printf("socket bind error \n");
return -1;
}
if(listen(sock,10)!=0) //set sock to listen
{
printf("error listening\n");
return -1;
}
printf("Waiting for connections....\n");
while(1)
{
newsock=accept(sock, (struct sockaddr*)NULL, NULL);
char temp[1000]="gggggg\n";
write(newsock,temp,strlen(temp));
write(newsock,temp,strlen(temp));
close(newsock);
sleep(1);
}
return 0;
}