recvfrom and timeout signal

[Christopher Faylor]

On Tue, Feb 19, 2002 at 11:51:59PM +0100, Piotr Stepien wrote:
>Christopher,
>
>Hope this working test case is small enough. I removed all unecessary code.
>Please let me know if you need anything else.

I wasn't asking for personal email.  That's precisely why I set the
Reply-To and Mail-Followup-To to go to the cygwin mailing list.

"Someone" does not necessarily mean me.

cgf

>-----Original Message-----
>From: cygwin-owner@cygwin.com [mailto:cygwin-owner@cygwin.com]On Behalf Of
>Christopher Faylor
>Sent: Tuesday, February 19, 2002 10:42 PM
>To: cygwin@cygwin.com
>Subject: Re: recvfrom and timeout signal
>
>
>On Tue, Feb 19, 2002 at 10:28:02PM +0100, Piotr St?pie? wrote:
>>Hi All,
>>
>>I try to implement timeout for recvfrom:
>>
>>	struct	sigaction action;
>>	action.sa_handler = alarm_signal;
>>	action.sa_flags = 0;
>>	sigemptyset(&(action.sa_mask)); 	/* ignore all known signals */
>>	sigaction(SIGALRM,&action,NULL);  	/* ensures that SA_RESTART is NOT set
>*/
>>
>>	alarm(TIMEOUT);
>>	int st=recvfrom(sockfd,buff,sizeof(buff),0,(sockaddr*)&srv_addr,&sz);
>>	if(st == -1){
>>		if(errno==EINTR){
>>			/* timeout */
>>		}else{
>>			alarm(0); /* reset alarm */
>>		}
>>	}
>>
>>but the process is never woken by SIGALRM when no packet is received.
>>The recvfrom waits forever.
>>
>>Has anybody an idea what can be wrong ?
>
>Nope.  Send an actual small working test case and someone will probably
>investigate it.
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#include<iostream.h>
#include<iomanip.h>

#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<arpa/inet.h>
#include<unistd.h>
#include<string.h>
#include<errno.h>
#include<sys/wait.h>
#include<signal.h>


#define BADSIGNAL ((void(*)(int))-1)
#define TIMEOUT 5


void err_dump(const char* msg){
	cerr << msg << ", errno=" << errno << endl;
	exit(1);
}

void alarm_signal(int){
	cout << "signal received\n";
	cout.flush();
}


int main(){
	struct sockaddr_in cli_addr,srv_addr;

	bzero( (char*)&srv_addr, sizeof(srv_addr) );
	srv_addr.sin_family = AF_INET;
	srv_addr.sin_addr.s_addr = inet_addr("255.255.255.255");
	srv_addr.sin_port = htons(192);

	bzero( (char*)&cli_addr, sizeof(cli_addr) );
	cli_addr.sin_family = AF_INET;
	cli_addr.sin_addr.s_addr = htonl(INADDR_ANY);
	cli_addr.sin_port = htons(0);

	int sockfd = socket(AF_INET,SOCK_DGRAM,0);//IPPROTO_UDP);
	if(sockfd == -1){
		err_dump("can't open socket");
	}
	{
	    int on=1;
	    if(setsockopt(sockfd,SOL_SOCKET,SO_BROADCAST,&on,sizeof(on))==-1){
		err_dump("error setsockopt");
	    }
	}

	if(bind(sockfd,(sockaddr*)&cli_addr,sizeof(cli_addr))== -1){
		err_dump("can't bind to port");
	}

	char buff[0x100];

/*** BEGIN AREA OF INTEREST ***/
	struct	sigaction action;
	action.sa_handler = alarm_signal;
	action.sa_flags = 0;
	sigemptyset(&(action.sa_mask)); 	/* ignore all known signals */
	sigaction(SIGALRM,&action,NULL);  	/* ensures that SA_RESTART is NOT set */
	int sz=sizeof(srv_addr);
	alarm(TIMEOUT);
	int st=recvfrom(sockfd,buff,sizeof(buff),0,(sockaddr*)&srv_addr,&sz);
/*** END AREA OF INTEREST ***/
 	if(st == -1){
	    if(errno==EINTR){
		cout << "timeout occured\n";
	    }else{
	        alarm(0);
		err_dump("error recvfrom");
	    }	    
	}
	close(sockfd);
	return 0;
}

-------------- next part --------------
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