Thread: blocking sockets and select

  1. #1
    Registered User
    Join Date
    Nov 2007

    blocking sockets and select


    I'm trying to fix a bug in tinyproxy 1.7.0 (old, dead project, I am trying to avoid an infinite blocking recv() call by using select first to test. I'm trying to do minimal changes to the code (so I don't want to make the socket non-blocking right from the get go). Hence this attempt at making an overloaded of sorts recv method.

    So where there would normally be:
    ret = recv(fd, buffer, SEGMENT_LEN, MSG_PEEK);

    I wish to use:
    ret = recv_timeout(fd, buffer, SEGMENT_LEN, MSG_PEEK);

    recv_timeout uses select to make sure the code won't hang on a recv, then goes and performs the recv as per normal. My attempt at doing this fails, select() always times out, it never returns even when there is data in the fd. What am I doing wrong with select?

    recv_timeout(int fd, void *buf, size_t len, int flags)
    	ssize_t ret;
    	struct timeval tv;
    	fd_set rset;
    	// init set
    	// add to set
    	FD_SET(fd, &rset);
            // So safe to assume I'm passing correct arguments
    	//ret = recv(fd, buf, len, flags);
    	//return ret;
            // this is set to 60 seconds
    	tv.tv_sec =
    	tv.tv_usec = 0;	
            // NEVER returns before the timeout value.
    	ret = select(fd, &rset, NULL, NULL, &tv);
    	if (ret == 0) {
    				    "Idle Timeout (after select)");
    		return 0;
    	} else if (ret < 0) {
    			    "recv_timeout: select() error \"&#37;s\". Closing connection (fd:%d)",
    			    strerror(errno), fd);
    	ret = recv(fd, buf, len, flags);
    	return ret;
    Advice? I know that the correct arguments are passed through, as I can change this method to go straight to recv(bypass select) and the proxy works as per normal (and still hangs if the recv blocks).
    Last edited by ecornips; 11-11-2007 at 03:53 PM. Reason: comments in code added

  2. #2
    Registered User
    Join Date
    Nov 2007
    I have found my problem. FWIW:

    ret = select(fd, &rset, NULL, NULL, &tv);


    ret = select(fd+1, &rset, NULL, NULL, &tv);

Popular pages Recent additions subscribe to a feed

Similar Threads

  1. Pros and Cons of blocking versus non-blocking sockets?
    By abachler in forum Networking/Device Communication
    Replies: 4
    Last Post: 05-08-2008, 06:52 AM
  2. program structure with select sockets
    By n3v in forum Networking/Device Communication
    Replies: 9
    Last Post: 06-03-2006, 06:34 AM
  3. multiple UDP sockets with select()
    By nkhambal in forum Networking/Device Communication
    Replies: 2
    Last Post: 01-17-2006, 07:36 PM
  4. Sockets and select()
    By xxx in forum Windows Programming
    Replies: 0
    Last Post: 11-18-2002, 03:06 PM
  5. Sockets - select()
    By Unregistered in forum C++ Programming
    Replies: 0
    Last Post: 08-28-2001, 06:22 AM