#1 2018-12-05 18:02:42

armstrap
Member
Registered: 2018-11-28
Posts: 9

Can't pair PC and smartphone with enabled router firewall

I have successfully installed General Sync on my Linux PC and Android Smartphone, after following your advice in a separate post - thank you. But I cannot get them to pair. They are both on the same local home network, downstream of the router (with inbuilt firewall). If I type 192.168.1.38:7962 on my PC browser, I get the message €(Human-readable identifier block expected, which you say means the PC sees the phone, but the other way round (192.168.1.36:7962 from phone to PC) results in 'This page isn't working - 192.168.1.36 sent an invalid response - ERR_INVALID_HTTP_RESPONSE.
What should I do?

#2 2018-12-05 19:12:36

ds
Founder / Developer
From: Freiburg, Germany
Registered: 2016-06-15
Posts: 222

Re: Can't pair PC and smartphone with enabled router firewall

I moved your post into a separate thread, as this forum is intended to keep different issues in different threads.

armstrap wrote:

ERR_INVALID_HTTP_RESPONSE

It is likely that the phone sees the PC if you get this response. Technically, the 'correct' response for GeneralSync is an 'invalid' response for a browser. So that's expected.

armstrap wrote:

What should I do?

If devices can connect to each other, but pairing doesn't work in both directions (that is, neither entering the PC's code on the phone nor entering the phone's code on the PC works), it is likely that a firewall or other network component blocks broadcasts. Broadcasts are special network packages used by GeneralSync to find other devices.

Check your router's firewall configuration about something blocking 'broadcast' or 'multicast' (or, 'all/other traffic'). While GeneralSync only uses the former, some firewalls front-ends do not differentiate between these two terms. Also check the firewall on the PC (you most likely have one) and on the smartphone (if you installed one).

If that does not help or you can't find a suitable setting, you could also attempt to temporarily disable one or more firewalls, and then re-attempt the pairing. That way you can identify which firewall(s) block GeneralSync's traffic.

It is also possible to disable the use of broadcasts in GeneralSync. However, that requires static IPs or DNS-resolveable hostnames to be set up in the router. As this requires basic knowledge about computer networks, most users should use broadcasts instead. To disable broadcasts:

  • In the settings on each device, enable 'Advanced Options' and type the IP or hostname of the device into the text field 'DNS-resolveable hostname'.

  • While pairing, in addition to entering the pair code, enter the IP or hostname of the other device into the text field 'DNS-resolveable hostname' in the pair dialog's 'Advanced Options'

#3 2018-12-06 15:17:22

armstrap
Member
Registered: 2018-11-28
Posts: 9

Re: Can't pair PC and smartphone with enabled router firewall

Thank you for the very quick response. I have now been able to sync my calendar across from the PC to my smartphone (it was syncing rather than pairing that was the issue, and un-powering and re-powering my router seemed to clear the fault), but I am still having problems with the address book. I clicked and dragged my contact list into the new book as you instructed, although it would only transfer about 50 entries at at time, and it won't transfer group lists. Now if I try to edit or delete a contact in the new address book on my PC I get a message telling me that 'An error occurred while communicating with General Sync; Application is not allowed to access this set'. I already have much the same set of contacts in my phone (via a different method), but when I deleted 1 entry there and tried to sync back to the PC as a test, the time stamp confirmed a sync happening but nothing changed in the PC address book.
Also, how often does the sync occur, and is it programmable? I really only need to do it once a day, or manually when needed. Is this possible?

#4 2018-12-06 19:00:44

ds
Founder / Developer
From: Freiburg, Germany
Registered: 2016-06-15
Posts: 222

Re: Can't pair PC and smartphone with enabled router firewall

armstrap wrote:

Now if I try to edit or delete a contact in the new address book on my PC I get a message telling me that 'An error occurred while communicating with General Sync; Application is not allowed to access this set'.

While I don't know what you did to end up like this, this error message means that Thunderbird is not registered correctly to receive/send address book data from/to GeneralSync. You should be able to fix that issue by removing the problematic address book from Thunderbird and re-creating it.

armstrap wrote:

Also, how often does the sync occur, and is it programmable?

The exact timing is rather complex and depends on many factors. As a rule of thumb, GeneralSync will sync roughly once per hour, whenever you make changes and after connecting to a local network (Android only).

On Android, you can change the sync frequency in the App's preferences. The corresponding setting is only visible if you enable advanced options through the action bar. To disable any form of synchronization, you can alternatively disable automatic Synchronization in Android's settings. There are both a global flag for all apps (usually called "Sync" or "Automatic Sync") and fine-grained flags for each individual Android account (in the "Accounts" category of Android's system settings). Please note that GeneralSync will not work correctly while automatic synchronization is disabled, even when manually starting a sync.

On PC, changing the synchronization frequency is currently not supported through the user interface. If that is important to you, it is possible to change the configuration in the underlying database using command line tools – but I would strongly recommend to keep the standard values.

On both platforms, it is also possible to manually force a sync. You find the button for that in the dashboard's "devices" section.


Note: if you are concerned about the battery impact on Android, it is usually a better idea to change the 'Wi-Fi Power Policy' in GeneralSync's settings to 'Protect sync operations, but permit permanent disconnect while sleeping' instead of tweaking the sync frequency. In most situations, that has the same battery impact as disabling automatic sync, but you still get some benefits of automatic synchronization.

#5 2018-12-07 17:23:57

armstrap
Member
Registered: 2018-11-28
Posts: 9

Re: Can't pair PC and smartphone with enabled router firewall

Thank you again for the quick response. I have now sorted out the problem with the address book as you suggested, by re-creating it, although please note that I still had to transfer batches of contacts across, as it wouldn't transfer them all in one go under 'SelectAll', and it does not work properly with groups of contacts (I have Thunderbird 60.2.1, which also required a new Lightning add-on to restore the calendar of previous versions).
I have also got the sync programming sorted to suit me (without disabling auto-sync), so I am delighted with the end result. My only concern now is how much the licence will cost in due course for simple one-to-one (PC to smartphone) private use!

#6 2018-12-07 23:59:10

ds
Founder / Developer
From: Freiburg, Germany
Registered: 2016-06-15
Posts: 222

Re: Can't pair PC and smartphone with enabled router firewall

armstrap wrote:

does not work properly with groups of contacts

Thanks for the report, copying address lists with the current version of the GeneralSync add-in (0.3.1.4b) seems to indeed fail in some cases, at least with the latest version of the GeneralSync Add-in. I'll try to publish a fix soon.

Regarding pricing: I'm not yet ready to publicly post anything more concrete than the basic licensing model (recurring fees with a clear separation between commercial and non-commercial use, as stated in the FAQ).
If you want, you can email me a rough outline of your usage (private/commercial/charity/..., number of devices, number of users) and whatever monthly fee you would consider reasonable for that. I can then give you some private feedback on your estimate.

#7 2018-12-12 12:03:26

armstrap
Member
Registered: 2018-11-28
Posts: 9

Re: Can't pair PC and smartphone with enabled router firewall

Hi. I'm afraid that I am still having problems with my address book - re-creating it did sort the original access denial, but at least 20% of the entries clicked and dragged across from my original Thunderbird address book (which worked fine) cannot be edited or even deleted - new entries seem to work OK, as do the remaining 80% of my total. If I transfer them back to TB, they are editable/deletable again so there does appear to be something amiss within the new GeneralSync address book. I don't fancy having to re-enter all the dodgy ones manually and my attempts at some sort of workaround have failed. Are you likely to be publishing a new GeneralSync add-in fairly soon?

#8 2018-12-12 15:33:27

ds
Founder / Developer
From: Freiburg, Germany
Registered: 2016-06-15
Posts: 222

Re: Can't pair PC and smartphone with enabled router firewall

armstrap wrote:

Are you likely to be publishing a new GeneralSync add-in fairly soon?

If you want, you can download Version 0.3.1.5b manually using this link. When downloading from Firefox, make sure to right-click the link and select 'save link as'.

You can manually install the xpi file in Thunderbird's add-on tab, using the gear icon above the list of installed add-ons.

armstrap wrote:

20% of the entries [...] cannot be edited or even deleted - new entries seem to work OK

I'm not sure if this is caused by the issue fixed in 0.3.1.5b. If the issue persists with the new version, open the error console (through Thunderbird's menu: "Tools | Developer Tools | Error Console"). Then attempt to delete or change an affected contact. There should be new messages popping up in the error console window. It would be great if you could post them here.

I'm sorry for the inconvenience.

#9 2018-12-18 17:18:36

armstrap
Member
Registered: 2018-11-28
Posts: 9

Re: Can't pair PC and smartphone with enabled router firewall

Eureka! Downloading and installing V 0.3.1.5b seems to have done the trick, so all is working fine now. Many thanks for your help.

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