Bad server version ProtocolErrorCode=209

As a bit of background: I have been working through a number of issues with my app which already uses realm sync (realmSwift 10.16.0). The issues, which mainly revolved around having an expired login token whereby users were not automatically logged out (along with destructive changes to my schema), have lead me to terminating sync, then reinstating the sync. I believe I have addressed these problems through testing in a test environment (which included upgrading to realmSwift 10.26.0), however, when I push these changes to my production environment I am now seeing the following error. The error occurs upon users re-logging in to the app (due to the expired token).

client file contained lastIntegratedServerVersion(8) greater than the downloadServerVersion(3) sent in the IDENT message which is not allowed (ProtocolErrorCode=209)

I am happy to troubleshoot myself, however, I don’t really know where to start with the above error, as the only mention I have been able to find of ProtocolErrorCode=209 is in: Integrating changesets failed: error finding the previous history size for version 80: client is disconnected (ProtocolErrorCode=101) - #4 by Mansoor_Omar.

I appreciate the suggestion in the above link to open a ticket, however, as I said, Im happy to debug this one myself with a few clues. Also, I should mention, I expect to be running in to a BadClientFileIdent error, which I believe I am already handling properly as per my test environment, as opposed to the ProtocolErrorCode=209.


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Just wanted to +1 this question, I’m having a similar issue which I posted about here: ERROR: client file contained lastIntegratedServerVersion greater than the downloadServerVersion – (ProtocolErrorCode=209)

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+1, seeing it happening in my app with Flexible Sync. Any way to solve this error that shows up in Realm’s logs?

+1 on this. Using flexible sync in Android (Java, realm v 10.11.0). Also seeing Bad server version (IDENT, UPLOAD) a lot and it makes the app do a client reset. Just any general explanation about this error would be hugely appreciated

Hi! If you DM me a link to your app I can investigate what’s going on here.

Hi there, I’m wondering if there are any updates regarding this issue. I’m seeing it in the app I’m working on as well - also using Flex Sync

Hi @Alexander_Sanchez,

There is a known issue in an old version of realm-core that could lead to these errors, which was resolved in v11.16.0. If you share which SDK are you using, and which version, we can determine if your app is using a version of realm that has this bug.