recvfrom重发定时SIGALRM并不能准时到来为什么?
	#define TIMEOUT 20/*20 seconds*/ truct sigaction sa_old; struct sigaction sa_new; nrtn=0; sa_new.sa_handler=sigalrm; sigemptyset(&sa_new.sa_mask); sigaddset(&sa_new.sa_mask,SIGALRM); sa_new.sa_flags=0; sigaction(SIGALRM,&sa_new,&sa_old); alarm(OUTTIMEVAL); if((nrtn=recvfrom(socket,pkgrcvbuff,nwilbercv,\ (blrcvpeek?MSG_PEEK:0)|MSG_WAITALL,\ (struct sockaddr*)&sockaddr,&sockaddrlen))<0) /* NULL,NULL))<0) */ { if(errno==EINTR) { alarm(0); sigaction(SIGALRM,&sa_old,NULL); return -2;/* time out */ } else { printf("client:recvfrom error %s.\n",strerror(errno)); alarm(0); sigaction(SIGALRM,&sa_old,NULL); return -1; } } alarm(0); sigaction(SIGALRM,&sa_old,NULL); static void sigalrm(int signo) { printf("TIME OUT.\n"); return;/* just interrupt the recvfrom() function */ }/* end sigalrm() */ 好像recvfrom一直阻塞了，不能被SIGALRM信号中断，只是偶尔能打印出TIME OUT来，也就是说不能 返回-2(return -2)进行重发。 在我这种情况下使用select定时不方便。怎么才能使SIGALRM按时的中断recvfrom实现自动重发呢，欢迎 ejiang指点，欢迎各位大虾指点。谢谢。 run brain
	Re: recvfrom重发定时SIGALRM并不能准时到来为什么?
	First of all, alarm() should work. I've tested it on my box. Your real problem is under Linux, the default sigaction's sa_flags is SA_RESTART, so recvmsg() will restart after your SIGALRM's handler. So, your current program will never reach "return -2". If you want to use alarm signal to interrupt your recvfrom() call, you need to specify the sa_flags = SA_INTERRUPT explicitly (Actually, in Linux's kernel, SA_INTERRUPT is ignored, so basically sa_flags = 0 should work too. But, specifiying it to SA_INTERRUPT is a good behavior to make your program be compatible with other platform) I don't know your kernel's version yet. Basically under linux2.2.x you can not use setsockopt() to specify the socket's SO_RCVTIMEO, as same RCVLOWAT ;), you do can do that in linux2.4.x. EJ ------------------------- There's no spoon - The Matrix -------------------------
	Re: recvfrom重发定时SIGALRM并不能准时到来为什么?
	linux kernel is 2.2.16-22 run brain