Go Premium for a chance to win a PS4. Enter to Win

x
?
Solved

Timeout

Posted on 2000-02-19
2
Medium Priority
?
2,026 Views
Last Modified: 2013-12-26
I am writing a echo server/client program in Unix.
I have executed the following statement to send and receive a UDP packet.

while (1) {
sendto(outFd, data, dataLength, 0, (struct sockaddr*)&outAddr, sizeof(outAddr))
int n = recvfrom(inFd, buffer, length, 0, (struct sockaddr*) &inAddr, &inAddLen
);

if (timeout)continue;
else break;
}

Since UDP is not reliable, so the recvfrom()sometimes never get back it echo. So I would like to add a timeout handle. If recvfrom() is timeout, then the program would go back to sendto() and send data again.

I know I should use signal and alarm. But what I should exactly add to my program so that when the recvfrom() time out, the signal handler would help me to "skip" the recvfrom() and do sendto() again?
0
Comment
Question by:matchz
2 Comments
 
LVL 3

Accepted Solution

by:
ufolk123 earned 600 total points
ID: 2539533
matchz,

better is you do not bet on signals and alarms.You can use select() which comes handy for this purpose.in select() call you can specify the timeout in millisec resoultion.So you can wait for some time and try sendto again if select returns timeout.
fd_set RecFd,ErrFd;
const struct timeval * timeout ;

/** Put app timeout values here ***/
timeout.tv_sec=0;
timeout.tv_use=0;
/****************************/

while (1) {
                   sendto(outFd, data, dataLength, 0, (struct sockaddr*)&outAddr, sizeof(outAddr)) ;
                   /*** Code for timeout **/
                  FD_SET(inFd, &RecFd)
                  FD_SET(inFd, &ErrFd)
                  select ( inFd+1, &RecFd,NULL,&ErrFd, &timeout);
                  if( FD_ISSET(inFd, &RecFd)  //OK
                      int n = recvfrom(inFd, buffer, length, 0, (struct sockaddr*) &inAddr, &inAddLen
                 else if( FD_ISSET(inFd, &ErrFd)  //Socket problem
                      /* Take action for sock error */
                 else // Timeout happened
                     break;
            );
 


This is just outline code.You may have to check return value of select() etc for catching all failure conditions.But on a whole you can use this construct to acheive you goal.


0
 

Author Comment

by:matchz
ID: 2547369
While I am seldom to write program on Unix perform. I know very less in Unix programming.
Thank you for your answer and my program work now!
^_^
0

Featured Post

Ask an Anonymous Question!

Don't feel intimidated by what you don't know. Ask your question anonymously. It's easy! Learn more and upgrade.

Question has a verified solution.

If you are experiencing a similar issue, please ask a related question

Introduction: Displaying information on the statusbar.   Continuing from the third article about sudoku.   Open the project in visual studio. Status bar – let’s display the timestamp there.  We need to get the timestamp from the document s…
Introduction: Dialogs (1) modal - maintaining the database. Continuing from the ninth article about sudoku.   You might have heard of modal and modeless dialogs.  Here with this Sudoku application will we use one of each type: a modal dialog …
This video will show you how to get GIT to work in Eclipse.   It will walk you through how to install the EGit plugin in eclipse and how to checkout an existing repository.
Look below the covers at a subform control , and the form that is inside it. Explore properties and see how easy it is to aggregate, get statistics, and synchronize results for your data. A Microsoft Access subform is used to show relevant calcul…
Suggested Courses

972 members asked questions and received personalized solutions in the past 7 days.

Join the community of 500,000 technology professionals and ask your questions.

Join & Ask a Question