From mboxrd@z Thu Jan 1 00:00:00 1970 Path: news.gmane.org!not-for-mail From: Paul Eggert Newsgroups: gmane.emacs.devel Subject: Re: Determining whether a TCP connection is up Date: Sat, 03 Aug 2013 07:09:47 -0700 Organization: UCLA Computer Science Department Message-ID: <51FD0F2B.5060605@cs.ucla.edu> References: NNTP-Posting-Host: plane.gmane.org Mime-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Trace: ger.gmane.org 1375539011 16457 80.91.229.3 (3 Aug 2013 14:10:11 GMT) X-Complaints-To: usenet@ger.gmane.org NNTP-Posting-Date: Sat, 3 Aug 2013 14:10:11 +0000 (UTC) To: emacs-devel@gnu.org Original-X-From: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Sat Aug 03 16:10:13 2013 Return-path: Envelope-to: ged-emacs-devel@m.gmane.org Original-Received: from lists.gnu.org ([208.118.235.17]) by plane.gmane.org with esmtp (Exim 4.69) (envelope-from ) id 1V5cX3-0005NO-IT for ged-emacs-devel@m.gmane.org; Sat, 03 Aug 2013 16:10:09 +0200 Original-Received: from localhost ([::1]:54337 helo=lists.gnu.org) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V5cX2-0005OC-R1 for ged-emacs-devel@m.gmane.org; Sat, 03 Aug 2013 10:10:08 -0400 Original-Received: from eggs.gnu.org ([2001:4830:134:3::10]:45208) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V5cWv-0005B6-2V for emacs-devel@gnu.org; Sat, 03 Aug 2013 10:10:07 -0400 Original-Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1V5cWo-0006vY-JM for emacs-devel@gnu.org; Sat, 03 Aug 2013 10:10:00 -0400 Original-Received: from smtp.cs.ucla.edu ([131.179.128.62]:53200) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1V5cWo-0006vG-DB for emacs-devel@gnu.org; Sat, 03 Aug 2013 10:09:54 -0400 Original-Received: from localhost (localhost.localdomain [127.0.0.1]) by smtp.cs.ucla.edu (Postfix) with ESMTP id AF6F6A6002D for ; Sat, 3 Aug 2013 07:09:53 -0700 (PDT) X-Virus-Scanned: amavisd-new at smtp.cs.ucla.edu Original-Received: from smtp.cs.ucla.edu ([127.0.0.1]) by localhost (smtp.cs.ucla.edu [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id ssEI7j3kCQzv for ; Sat, 3 Aug 2013 07:09:52 -0700 (PDT) Original-Received: from [192.168.1.9] (pool-71-108-49-126.lsanca.fios.verizon.net [71.108.49.126]) by smtp.cs.ucla.edu (Postfix) with ESMTPSA id B5810A60023 for ; Sat, 3 Aug 2013 07:09:52 -0700 (PDT) User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130623 Thunderbird/17.0.7 In-Reply-To: X-Enigmail-Version: 1.5.2 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.6.x X-Received-From: 131.179.128.62 X-BeenThere: emacs-devel@gnu.org X-Mailman-Version: 2.1.14 Precedence: list List-Id: "Emacs development discussions." List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Original-Sender: emacs-devel-bounces+ged-emacs-devel=m.gmane.org@gnu.org Xref: news.gmane.org gmane.emacs.devel:162402 Archived-At: On 08/03/2013 05:30 AM, Lars Magne Ingebrigtsen wrote: > Is there a general TCP way > to probe for a connection? Can we (for instance) send a TCP KEEPALIVE > once and see whether we get anything back within (say) a second? I'm afraid not, since TCP keepalives won't work through proxies. See, for example, the first FAQ in http://www.proftpd.org/docs/howto/KeepAlives.html