# Linux app cannot connect to server
**URL:** https://forum.pydio.com/t/linux-app-cannot-connect-to-server/3571
**Category:** Sync Client
**Tags:** linux
**Created:** [November 9, 2020, 7:46pm UTC](https://forum.pydio.com/t/linux-app-cannot-connect-to-server/3571 "2020-11-09T19:46:40Z")
**Posts on this page:** 4
**Page:** 1
### Author:  [@thenoots](https://forum.pydio.com/u/thenoots)
#### Post date: [November 9, 2020, 7:46pm UTC](https://forum.pydio.com/t/linux-app-cannot-connect-to-server/3571/1 "2020-11-09T19:46:40Z")
Hi!
I’m running a dockerized Pydio Cells Home Edition 2.1.6-ls25 server behind an nginx reverse proxy with a certificate from let’s encrypt.
The web browser functionalities work ok, but I’m not able to get the cells sync linux app to connect to the server.
1. I authenticate successfully
2. When I create the first sync task and try to choole the remote folder, the app says “cannot connect (connection refused): there may be an issue with the SSL certificate”.
There is no issue with the certificate, yet the client cannot connect to the server.
TLS offloading is done in the reverse proxy, which manages the LE certificates.
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### Author:  [@bsinou](https://forum.pydio.com/u/bsinou)
#### Post date: [November 10, 2020, 5:42am UTC](https://forum.pydio.com/t/linux-app-cannot-connect-to-server/3571/2 "2020-11-10T05:42:01Z")
Hello @thenoots
> [@thenoots](#):
>
> TLS offloading is done in the reverse proxy, which manages the LE certificates.
I think your problem is here: the Sync client communicates with the server via gRPC that is based on HTML2.
This protocol does not accept TLS offloading between the client and the server: you must use TLS from end to end or no TLS at all.
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### Author:  [@thenoots](https://forum.pydio.com/u/thenoots)
#### Post date: [November 10, 2020, 4:23pm UTC](https://forum.pydio.com/t/linux-app-cannot-connect-to-server/3571/3 "2020-11-10T16:23:51Z")
I don’t have gRPC enabled on the server and the port is not forwarded in the firewall. I didn’t know that gRPC is a requirement for the desktop client.
Is it a requirement for the Android app also?
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### Author:  [@thenoots](https://forum.pydio.com/u/thenoots)
#### Post date: [November 12, 2020, 5:23pm UTC](https://forum.pydio.com/t/linux-app-cannot-connect-to-server/3571/4 "2020-11-12T17:23:30Z")
Turns out that pydio-cells was actually running in tls mode with a self signed certificate generated by the [linuxserver.io](http://linuxserver.io) entrypoint script: [https://github.com/linuxserver/docker-pydio-cells/blob/master/root/etc/cont-init.d/30-config](https://github.com/linuxserver/docker-pydio-cells/blob/master/root/etc/cont-init.d/30-config)
Because the self signed certificate had a different SAN (pydio-cells) than the public name I gave to the cells-sync client during login, there was another error. I fixed that by setting the $SERVER\_IP variable to the same fqdn on which the reverse proxy hosts the application.
Now, there is another issue - I see a lot of errors like this one during synchronization:
`2020-11-12T19:11:59.192+0200 ERROR sync-task Error while transferring file {"NodePath": "test-folder/temp/CAM00005.jpg", "target": "fs:///opt/storage/temp/pydio"}`
`2020-11-12T19:11:59.192+0200 ERROR sync-task Status: Error while transferring file (Last-Modified time format not recognized. Please report this issue at https://github.com/pydio/minio-go/issues.) - retrying...`
`2020-11-12T19:11:59.195+0200 ERROR systray http://localhost:3636/static/js/main.d5710352.chunk.js? __WB_REVISION__ =0f7d77698fb381447a3e:1:142123: CONSOLE LOG [object Object]`
`2020-11-12T19:12:00.025+0200 ERROR sync-task Cannot get reader on source {"job": "create", "path": "test-folder/temp/CAM00012.jpg", "error": "Last-Modified time format not recognized. Please report this issue at https://github.com/pydio/minio-go/issues."`
Seems like these errors happen only for image files as these file types don’t sync from the server.
But they sync ok from my computer to the server.
Other files have synchronized ok both ways.