Mail Archives: cygwin/2003/11/03/02:04:17
I set a timeout for recvfrom() by calling select() on a UDP socket:
socket()=>sendto()=>select()=>recvfrom().
It seems that it need not call bind() or connect() for UDP socket here.
This method is recommended by
"UNIX Network Programming Volum1 Networking APIs: Sockets and XTI(Second Edition)", W.Richard Stevens
Chapter 13 section 2.
source code:
http://www.cs.odu.edu/~cs779/stevens2nd/lib/readable_timeo.c
http://www.cs.odu.edu/~cs779/stevens2nd/advio/dgclitimeo.c
>> if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0){
>> fprintf(stderr, "cannot open socket for udp packet!\n");
>> exit(1);
>> }
>>
>> while(1){
>> struct timeval tv;
>> fd_set fds;
>> radius_send(sockfd, NULL, secret);
>> FD_ZERO(&fds);
>> FD_SET(sockfd, &fds);
>>
>> tv.tv_sec = timeout;
>> tv.tv_usec = 0;
>> printf("select the socket_fd : d, thread_id is : d\n",
>> sockfd, tid);
>> if((ret=select(sockfd + 1, &fds, NULL, NULL, &tv))==1)
>> *rep = radius_recv(sockfd);
>> ...
This test code is cut from a multi-thread radius(Authentication,Accounting protocol,UDP) client.
if radius thread count > 18,some thread's select() will take 100% CPU in cygwin envirionment,
but the same code work ok in solaris and linux envirionment.
>On Fri, Oct 31, 2003 at 01:14:17PM +0800, zhouxin wrote:
>> Cygwin implementation of select() take 100 CPU under multi-thread environment sometimes.
>> [...]
>> if((sockfd = socket(AF_INET, SOCK_DGRAM, 0)) < 0){
>> fprintf(stderr, "cannot open socket for udp packet!\n");
>> exit(1);
>> }
>>
>> while(1){
>> struct timeval tv;
>> fd_set fds;
>>
>> FD_ZERO(&fds);
>> FD_SET(sockfd, &fds);
>>
>> tv.tv_sec = timeout;
>> tv.tv_usec = 0;
>> printf("select the socket_fd : d, thread_id is : d\n",
>> sockfd, tid);
>> select(sockfd + 1, &fds, NULL, NULL, &tv);
>> }
>
>That's not allowed. What is the select call waiting for? You
>didn't bind or connect it.
>
>Corinna
>
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>Corinna Vinschen Please, send mails regarding Cygwin to
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