Skip to main content
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [List Home]
Re: [paho-dev] Long timeouts to real sites with no MQTT
Hi all, thanks for the great info.  Nick and Roger, I trued the timing command you posted, and like Dave I am on Ubuntu for development and get the same values as Roger.  If this were just a desktop app, a minute wait wouldn't be something I was too concerned about, but the target is Android as well, and on the mobile a minute is a long time (and sometimes it lasts longer on the android.  I will have to see if I can get similar timings from the Android when on 3G).  

Regardless, Dave, I do think I will file a change request on bugzilla, but will investigate a bit before hand.  You actually gave me a workaround in your post as well.  What I plan on doing is pre-testing the connection with my own Socket using the connect() with a timeout parameter.  If it succeeds, then connect via Paho.  Initial tests indicate it will work.  So thanks for the great info.

Steve

p.s.  I modified the emails below so they didn't duplicate too much, hope noone minds I edited their content by removing quoted text. 


On Tue, Feb 26, 2013 at 6:14 AM, <paho-dev-request@xxxxxxxxxxx> wrote:
Date: Tue, 26 Feb 2013 09:47:44 +0000
From: "Nicholas O'Leary" <nick.oleary@xxxxxxxxx>
To: General development discussions for paho project
        <paho-dev@xxxxxxxxxxx>
Subject: Re: [paho-dev] Long timeouts to real sites with no MQTT
Message-ID:
        <CAF=vhqeV0=u-HQW-PX1nPq8XFAydwF_Jp=vrYS7uCX5LGWRwaA@xxxxxxxxxxxxxx>
Content-Type: text/plain; charset="iso-8859-1"

Hi Steven,

The connection timeout is there for when a socket is successfully
connected but the other end doesn't respond to the initial MQTT
connect packet exchange in a timely fashion.

I've run your code a few times and it times out for my after roughly
5-6 seconds:

nol@noltop:/tmp/Mqttv3ClientOut/ship$ java -classpath
org.eclipse.paho.client.mqttv3.jar:. SuperSimple
(00:05.624)Exception: Unable to connect to server

I get exactly the same results when I change the code to remove the
MqttClient altogether and just try to connect a raw socket (code
attached). Could you give that a go and see what you get?

I also get the same result when I simply try telnet'ing to that server/port:

nol@noltop:~$ time telnet some.company.net 1883
Trying 82.98.86.161...
telnet: Unable to connect to remote host: Connection refused

real 0m6.121s
user 0m0.000s
sys 0m0.000s



What operating system are you running this on? I suspect there is an
underlying socket level timeout coming into play here.

Cheers,
Nick

On 26 February 2013 03:29, Steven Luke <stevejluke@xxxxxxxxx> wrote:
> When I make a connection to a valid looking Host Address, but which does not
> have an MQTT server running I get a seriously long timeout (I think it may
> actually never end in some cases).  I tried setting the Connection Timeout
> to 20, or 5, or anything, but it doesn't work.  Anything I can try to make
> the client realize the connection is no-good earlier?  Alternatively is
> there something I can manually do in another thread to make the connection
> stop trying?
>
> This is a big issue for me, because the setting will be user-configurable
> and if it takes this long to fail it means a negative and very visible user
> experience.  I would like it to fail in 30 seconds or less so I can prompt
> for them to modify the address without making them wait for minutes to set
> up.
>
> Thanks,
> Steve
>
> Here is sample code which shows the problem.  In plain desktop Java it takes
> a consistent 1 minute, 3 seconds to fail.  I use the same code on android,
> and on WiFi it takes about the same time (a little over a minute), but on
> 3G/4G it takes 2+ minutes, and I timed one (google.com) at >10 minutes
> before killing it.
>
> public class SuperSimple
> {
>     public static final String timeDiffFormat = "%1$tM:%1$tS.%1$tL";
>     private static MqttClient client;
>
>     public static void main(String... args)
>     {
>         final long startTime = System.currentTimeMillis();
>         try
>         {
>             client = new MqttClient("tcp://some.company.net:1883",
> "this_should_fail_fast");
>
>             MqttConnectOptions mOptions = new MqttConnectOptions();
>             mOptions.setKeepAliveInterval(20);
>             mOptions.setConnectionTimeout(20);
>             client.connect(mOptions);
>
>         }
>         catch (MqttException mEx)
>         {
>             long errorTime = System.currentTimeMillis();
>             Date difference = new Date(errorTime - startTime);
>             String time = String.format(Locale.US, timeDiffFormat,
> difference);
>             String message = mEx.getMessage();
>             System.out.printf("(%s)Exception: %s%n", time, message);
>         }
>
>         try
>         {
>             client.disconnect();
>         }
>         catch (MqttException e)
>         {
>             //This always happens: already disconnected.
>         }
>     }
> }
>
>
> _______________________________________________
> paho-dev mailing list
> paho-dev@xxxxxxxxxxx
> http://dev.eclipse.org/mailman/listinfo/paho-dev
>
-------------- next part --------------
A non-text attachment was scrubbed...
Name: SocketTest.java
Type: application/octet-stream
Size: 724 bytes
Desc: not available
URL: <http://dev.eclipse.org/mailman/private/paho-dev/attachments/20130226/9dca35b4/attachment.obj>

------------------------------

Message: 4
Date: Tue, 26 Feb 2013 10:32:40 +0000
From: Roger Light <roger@xxxxxxxxxx>
To: General development discussions for paho project
        <paho-dev@xxxxxxxxxxx>
Subject: Re: [paho-dev] Long timeouts to real sites with no MQTT
Message-ID:
        <CAH7zdychRm125fwf44TRqNBkXw-zQ71RAsr=RyQRaj6j3q7xPw@xxxxxxxxxxxxxx>
Content-Type: text/plain; charset=UTF-8

On Tue, Feb 26, 2013 at 9:47 AM, Nicholas O'Leary <nick.oleary@xxxxxxxxx> wrote:

> nol@noltop:~$ time telnet some.company.net 1883

I got the below on Ubuntu Linux.

telnet: Unable to connect to remote host: Connection timed out

real    1m3.235s
user    0m0.000s
sys     0m0.008s

This can be controlled on a computer wide basis with
/proc/sys/net/ipv4/tcp_syn_retries - setting to "2" gave me a timeout
of about 7 seconds. This does affect other applications of course.

The suggestions I've just seen for C code is to set the socket
non-blocking before a connect(), then use select() or similar to wait
for the connection with a timeout. I'll be looking at that for my own
code!

Cheers,

Roger


------------------------------

Message: 5
Date: Tue, 26 Feb 2013 11:13:56 +0000
From: Dave Locke <locke@xxxxxxxxxx>
To: General development discussions for paho project
        <paho-dev@xxxxxxxxxxx>
Cc: paho-dev-bounces@xxxxxxxxxxx
Subject: Re: [paho-dev] Long timeouts to real sites with no MQTT
Message-ID:
        <OFDC93ADD0.50967E5B-ON80257B1E.003CF6D0-80257B1E.003DB7E3@xxxxxxxxxx>
Content-Type: text/plain; charset="us-ascii"

The Java client creates a socket and connects using the SocketFactory
createSocket(host, port)method.    It is possible to use the SocketFactory
to create a socket but not connect and then set a timeout on the
socket.connect() method that will cause the connect to timeout if it does
not succeed (or fail) before the timeout.   If this would be useful please
raise a request on the paho bugzilla


All the best
Dave

...

Unless stated otherwise above:
IBM United Kingdom Limited - Registered in England and Wales with number
741598.
Registered office: PO Box 41, North Harbour, Portsmouth, Hampshire PO6 3AU
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://dev.eclipse.org/mailman/private/paho-dev/attachments/20130226/d878fce8/attachment.html>

------------------------------

_______________________________________________
paho-dev mailing list
paho-dev@xxxxxxxxxxx
http://dev.eclipse.org/mailman/listinfo/paho-dev


End of paho-dev Digest, Vol 14, Issue 7
***************************************

Back to the top