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Full Discussion: Socket Keep-Alive
Top Forums Programming Socket Keep-Alive Post 302971952 by Corona688 on Wednesday 27th of April 2016 12:30:34 PM
Old 04-27-2016
All right, this loop is suspect:

Code:
    while ((size = recv(sock, recv_buf,
        RECV_BUFFER_SIZE, 0)) > 0)
    {
        recv_buf[size] = '\0';
        response.append(recv_buf);
    }

From man recv:

Code:
       When a stream socket peer has performed an orderly shutdown, the return
       value will be 0 (the traditional "end-of-file" return).

So, your program downloads the entire page, but doesn't stop there -- it calls recv() one more time when the transfer is done, which hangs until the web server becomes impatient and kicks you. Which is mecifully much less than the many minutes TCP usually defaults to. Then your program declares the download finished, writes another request to the dead socket, and "receives" another EOF in reply.

Reading until EOF might make sense without keepalives, but obviously won't do for persistent connections -- TCP/IP doesn't have an EOF signal, just an end of connection signal. This is why the web server must warn you of the content's length somehow -- as a content-length header, as chunked sections preprended with lengths in hexadecimal, etc.

Last edited by Corona688; 04-27-2016 at 01:47 PM..
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Socket(3pm)						User Contributed Perl Documentation					       Socket(3pm)

NAME
Coro::Socket - non-blocking socket-I/O SYNOPSIS
use Coro::Socket; # listen on an ipv4 socket my $socket = new Coro::Socket PeerHost => "localhost", PeerPort => 'finger'; # listen on any other type of socket my $socket = Coro::Socket->new_from_fh (IO::Socket::UNIX->new Local => "/tmp/socket", Type => SOCK_STREAM, ); DESCRIPTION
This module is an AnyEvent user, you need to make sure that you use and run a supported event loop. This module implements socket-handles in a coroutine-compatible way, that is, other coroutines can run while reads or writes block on the handle. See Coro::Handle, especially the note about prefering method calls. IPV6 WARNING This module was written to imitate the IO::Socket::INET API, and derive from it. Since IO::Socket::INET does not support IPv6, this module does neither. Therefore it is not recommended to use Coro::Socket in new code. Instead, use AnyEvent::Socket and Coro::Handle, e.g.: use Coro; use Coro::Handle; use AnyEvent::Socket; # use tcp_connect from AnyEvent::Socket # and call Coro::Handle::unblock on it. tcp_connect "www.google.com", 80, Coro::rouse_cb; my $fh = unblock +(Coro::rouse_wait)[0]; # now we have a perfectly thread-safe socket handle in $fh print $fh "GET / HTTP/1.015121512"; local $/; print <$fh>; Using "AnyEvent::Socket::tcp_connect" gives you transparent IPv6, multi-homing, SRV-record etc. support. For listening sockets, use "AnyEvent::Socket::tcp_server". $fh = new Coro::Socket param => value, ... Create a new non-blocking tcp handle and connect to the given host and port. The parameter names and values are mostly the same as for IO::Socket::INET (as ugly as I think they are). The parameters officially supported currently are: "ReuseAddr", "LocalPort", "LocalHost", "PeerPort", "PeerHost", "Listen", "Timeout", "SO_RCVBUF", "SO_SNDBUF". $fh = new Coro::Socket PeerHost => "localhost", PeerPort => 'finger'; AUTHOR
Marc Lehmann <schmorp@schmorp.de> http://home.schmorp.de/ perl v5.14.2 2012-04-13 Socket(3pm)
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