[mcgargle]

iNavX is great, but I have found a network bug on the iPad IOS 3.2, iNavX v3.1.6.

When I try to download a new NOAA chart while connected via wifi, more often than not iNavX will sit there for a few minutes and then say:

"Warning Unable to Download ... (timed out)"

The download is successful about 2/5 times.

The bug is exacerbated when I try to download multiple charts, for example selecting "Yes, All USA East". The first one or two charts download, then the connection times out again.

I have tried multiple wifi networks on different days in various locations, with identical results.

The same iNavX version on my iPhone, connected to the same wifi network, works fine.

HOWEVER, if I turn off wifi on the iPad and turn on cellular data, IT WORKS CORRECTLY WITH NO DELAY AND NO TIMEOUTS!

Hence, it seems likely that iNavX is having trouble making a network connection. Presumably this is in the network code, and the packets are never moving down the TCP/IP stack.

In order to test this, I installed Firewall IP. The problem was unchanged but, interestingly, Firewall IP never pops up a message about an outgoing connection on the occasions that iNavX is timing out, lending support to the notion that the iNavX software is failing to generate any packets. On the times that iNavX does not time out, Firewall IP correctly pops up a rule box, and then the chart download proceeds normally once I have allowed the connection.

The problem is severe because it is making it very difficult to download all of the NOAA charts for an area.

[mcgargle]

Oh, yes, also: re-syncing with iTunes makes no difference.

[GPSNavX]

iNavX relies on iOS to download the charts from the NOAA server. It makes no differentiation if it's a WiFi or cell connection or iPhone or iPad or version of iOS. The time out is set at 30 seconds which should be plenty for both types of network connections. I wonder why it's taking a few minutes before iNavX gives up trying to download the chart.

Do recommend you update to iOS 3.2.2 for your iPad in case there was any changes by Apple in the network stack.

Using iPad/iNavX 3.1.6 and a WiFi connection (802.11N) I was just able to download all the NOAA East Coast charts without issue. Also no reports from iNavX users having difficulty with WiFi downloads. Once in a while I will get a report of difficulty with a cell connection. To be expected with AT&T's sometimes very challenged network.

One thing you could try is accessing the NOAA website on your iPad with Safari and see if it loads consistently ..

http://www.charts.noaa.gov/RNCs/RNCs.shtml

[mcgargle]

Thanks for the quick response.

OK, iNavx is timing out after precisely 30 seconds, measured carefully. A "few minutes" was very imprecise--sorry.

The NOAA website is, at times, taking longer than 30 seconds to respond in my iPad's browser, even to display the user agreement page (which is just text). All other websites that I have tested are working fine, including other .gov domains.

Perhaps some sort of traffic shaping is at play, since I have tried 4-5 different providers. I am out of the country at the moment. No idea why cellular data works flawlessly (the opposite to what you would expect).

Firewall IP is supposed to optionally block outgoing connections. Either it is not doing so, or else iNavx is genuinely not initiating packet traffic.

Given the results of the browser test, I am doubtful that Firewall IP is working as advertised. Instead, it seems like iNavX is often timing out before the NOAA server can respond.

It seems like a longer timeout (or a user settable one) would be a good idea. Is there a place I can change the network timeout?

[mcgargle]

Also: when I access the NOAA server from a computer other than the iPad, but over the same internet connection, the response is consistently fast, with no measurable delay.

So it must be something specific to the iPad.

[mcgargle]

Update: I installed Network Ping for IOS and pinged a host that does not exist on my lan (and therefore cannot possibly send reply packets).

Firewall IP popped up instantaneously when I sent a ping, but it does not do so with iNavX on the occasions that iNavX times out.

On the occasions that iNavX successfully downloads a chart, Firewall IP consistently asks if it is OK to make the connection, and, once affirmed, the chart downloads.

This is strong evidence that, while there may sometimes be a delay of more than 30 seconds contacting the NOAA server from my iPad, iNavX is, at times, not even trying to contact it.

I'll try to put a packet sniffer on the lan and have a look.

[AugustH]

I suspect it's a bug in the iPad Wi-Fi driver. Sitting here on my net I can physically see the DSL router (hooked to my Airport Extreme), and when I pull up Mail on the iPad it says "checking for mail" and the router is showing no activity at all going in or out. Then after a long long delay (greater than 30 seconds!) there's some activity and Mail updates. This sounds like a DNS issue where the iPad isn't resolving the server's IP address. There's no way to set the DNS server on the iPad that I can see, so it must be getting it from the router (if set).

I am interested in seeing what your packet analyzer sees, especially for resolving the server names.

[GPSNavX]

Can't one set the DNS in the "DHCP" tab of the selected "Network"? I have heard "8.8.8.8" and "8.8.4.4" which is Google public DNS works well. I use those on my Mac, but have not tried on iPad/iPhone. I read using those for Apple TV helped improve Netflix streaming.

[AugustH]

Hmm yes you are right, if you tap on the '>' arrow next to the Wi-Fi network you can set the DNS. I have mine set to 8.8.8.8 (google!) but I think the other one is 4.4.4.4 (not sure though). So the DNS is set (for me it comes from the router, via DHCP) but Mail is still occasionally slow on network access. Other times it's not. Curious.

[mcgargle]

Well, that was a success!

I changed the DNS to 8.8.8.8. iNavX (v 3.1.7 now) went through about two-thirds of the East Coast charts before timing out again. This is a vast improvement. (I tested right before the change to make sure the bug was still active; it was--couldn't download anything.)

The view from the wifi router indicated very little packet traffic during the time out (haven't had time to do any analysis yet).

This looks to be consistent with a DNS failure: iPad sends a DNS request; no packet returned; iPad waits >30sec to retransmit; iNavX times out; firewall doesn't flag the traffic because it's just DNS traffic. That makes perfect sense.

Thank-you for the suggestions.

Maybe the workaround should go in the FAQ, since it is likely to affect all iPads.

Might also be worthwhile either adjusting that time out value or making it user settable; sailors end up sticking their resolvers into some strange domain name servers!