topic Re: Sync error: Illegal start of token [<] in ArcGIS Collector Questions

Sync error: Illegal start of token [<]

PaulBoehnlein — Sat, 27 Sep 2014 23:34:24 GMT

Trying to sync a feature service with offline edits in Collector and receiving the error "Illegal start of token [<]". Service has subtypes, domains and editor tracking. Hosted in a ArcGIS Online web map. Can anyone help with this?

Re: Sync error: Illegal start of token [<]

DavideContin — Thu, 23 Oct 2014 12:52:21 GMT

I have found the same problem with iOS Collector using a map containing some protected services hosted in our own server; from the company network we have no problem syncing the new features but with external connection (wifi or mobile) the synchronization fails with error: "Illegal start of token [<]"

Is this a firewall problem or something else? Anyone know how come does this error happen?

Re: Sync error: Illegal start of token [<]

GaryMorris1 — Thu, 23 Oct 2014 17:43:03 GMT

It might be a problem with the Web Adaptor used when you run Server for ArcGIS on your own host. If you are still having this problem please open a support ticket with Esri support. The more support calls Esri gets on this, the more it will help collect enough information to solve the problem.

The technical reason for the "Illegal start of token" message is that the server (or web adaptor) is responding with an HTML error page (which starts with "<") when the app is expecting JSON reply. Some users have used wireshark or Charles to view the HTML to find out what error was reported.

Re: Sync error: Illegal start of token [<]

Sravan_KumarUddarraju — Fri, 31 Oct 2014 19:55:15 GMT

I have had this issue because field type is blob for on one of the layer that are participating in featurelayer. Deleting blob field resolved the "illegal start of token" issue.

Re: Sync error: Illegal start of token [<]

DavideContin — Sat, 01 Nov 2014 17:04:46 GMT

This is our experience:

With iOS (iPone 4) the sync with external and internal connection works without problems.

With iOS (iPad Air) or Android (Samsung S4 Active) Collector using a map containing some protected services hosted in our own server; from the company network we have no problem syncing the new features but with external connection (wifi or mobile) the synchronization fails with error: "Illegal start of token [<]" (error visible only in iOS, Android doesen't show any error but ends without sync)

We overcame the problem with the port 6080 bypassing the Web Adaptor (adding :6080 to the link of the rest services) but it would be better to understand why this error is generated for iOS (iPad Air) or Android (Samsung S4 Active) but not for iOS (iPone 4); I have opened a technical issue to Esri support.

Re: Sync error: Illegal start of token [<]

SanneMikkelsen — Tue, 11 Nov 2014 10:06:55 GMT

Im having the same problem in Explorer for ArcGIS ver. 10.2.7. on an Ipad Air.

Re: Sync error: Illegal start of token [<]

AdrianMarsden — Tue, 25 Nov 2014 14:03:59 GMT

I'm geting this too - but ONLY when the basemaps I am using offline are my own, stored on the iPhone 5.

My basemap is of the same projection as my data, but NOT the same as the esri ones.

Is this likely to be an issue?

Re: Sync error: Illegal start of token [<]

AdrianMarsden — Wed, 26 Nov 2014 14:24:54 GMT

More research and it appears to work when I have a layer that has not been enabled for attachments, but fails as soon as I enable it for attachments.

Re: Sync error: Illegal start of token [<]

PaulBoehnlein — Thu, 11 Dec 2014 18:41:59 GMT

I never fully resolved this problem, but did reduce the frequency of the error by increasing the service timeout lengths.

Re: Sync error: Illegal start of token [<]

SamH — Wed, 22 Apr 2015 16:48:48 GMT

I am currently having this problem, getting the same error message "Sync Error an error occurred while synchronizing edits - illegal start of token [<]" Did anyone ever manage to resolve this issue ?

Re: Sync error: Illegal start of token [<]

MiaogengZhang — Wed, 22 Apr 2015 22:05:29 GMT

This issue could be related to network. If you are using Web Adapter, try to increased the uploadReadAheadSize value on IIS and sometimes that was enough to fix the issue

Launch “Internet Information Services (IIS) Manager”
Select the site that you are hosting your web application under it.
In the Features section, double click “Configuration Editor”
Under “Section” select: system.webServer then serverRuntime
Modify the “uploadReadAheadSize” section

Re: Sync error: Illegal start of token [<]

MiaogengZhang — Fri, 24 Apr 2015 23:27:56 GMT

In iOS, you will meet this error if you have a Server feature service added as an item with stored credentials in ArcGIS Online. The feature service has attachment enabled. Then you add picture attachment made from photo library instead of camera.

Re: Sync error: Illegal start of token [<]

danbecker — Wed, 29 Apr 2015 20:04:39 GMT

We have experienced a variety of token related errors on both iOS and Android collector versions, including 10.3.

Unable to download a map for offline use, unable to sync edits made on the device, ect...

In all cases, it was a result of:

1. feature service published on our own ArcGIS Server ver. 10.3

2. feature service credentials stored with the item when it's added to AGOL

Simply add the item to AGOL without storing the service credentials and the "token" problems are gone. Only downfall is having to login to BOTH collector AND the feature service.

We've simply created ArcGIS Server username/passwords to match our AGOL named user accounts, then field staff never get confused. They see a credential prompt and enter the same info.

Re: Sync error: Illegal start of token [<]

BledarBirbo1 — Wed, 06 May 2015 14:51:26 GMT

Sorry.

What does this error have to do with the kind of IMAGE that the user has selected. ?

Re: Sync error: Illegal start of token [<]

WilliamMcInnes — Mon, 22 Jun 2015 15:48:58 GMT

Is there any way to resolve this error so that the user can sync?

Re: Sync error: Illegal start of token [<]

BledarBirbo1 — Mon, 22 Jun 2015 15:59:00 GMT

Hi William.

We found that a fast network connection (UPLOAD SPEED) can fix this error.

Hope this helps.

Re: Sync error: Illegal start of token [<]

WilliamMcInnes — Mon, 22 Jun 2015 16:08:09 GMT

Thanks, we are on a satellite connection that can be slow at times. We will try to upload when traffic on our network is low.

Re: Sync error: Illegal start of token [<]

Gisbert61 — Tue, 10 Jan 2017 13:49:38 GMT

Yep, could be network traffic related. I had this while at the same time downloading another map. After that was finished synchronising was flawless.

Re: Sync error: Illegal start of token [<]

ronaldbruzzese — Thu, 02 Mar 2017 20:47:34 GMT

Miaogeng,

What did you increase the “uploadReadAheadSize” to?

Thanks

Re: Sync error: Illegal start of token [<]

MiaogengZhang — Thu, 02 Mar 2017 21:04:35 GMT

You can start with ~20MB and adjust it.