# Ubuntu Android problem **URL:** \ **Category:** Help\ **Created:** [October 2, 2021, 10:58am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674 "2021-10-02T10:58:34Z")\ **Posts on this page:** 20\ **Page:** 1
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 10:58am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/1 "2021-10-02T10:58:34Z")
Hello everyone. It would be really helpful to know how to do this on an Ubuntu server, because Android \<7.1.1 clients cannot connect anymore. ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 11:07am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/2 "2021-10-02T11:07:12Z")
Hi @bazar welcome to the LE community forum 🙂 Please tell us more details about this problem. What is the FQDN having trouble? Which version of Ubuntu? Which version of OpenSSL? Which port(s) are they having trouble connecting to? ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 11:18am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/3 "2021-10-02T11:18:59Z")
Thank you for prompt response. Here are the answers: [api.simlr.net](http://api.simlr.net) Ubuntu 18.04.6 LTS OpenSSL 1.1.1 port 443 ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 11:36am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/4 "2021-10-02T11:36:16Z")
I don't see anything obviously wrong with the cert there: ```nohighlight openssl s_client -connect api.simlr.net:443 -servername api.simlr.net CONNECTED(00000005) depth=2 C = US, O = Internet Security Research Group, CN = ISRG Root X1 verify return:1 depth=1 C = US, O = Let's Encrypt, CN = R3 verify return:1 depth=0 CN = api.simlr.net verify return:1 --- Certificate chain 0 s:CN = api.simlr.net i:C = US, O = Let's Encrypt, CN = R3 1 s:C = US, O = Let's Encrypt, CN = R3 i:C = US, O = Internet Security Research Group, CN = ISRG Root X1 2 s:C = US, O = Internet Security Research Group, CN = ISRG Root X1 i:O = Digital Signature Trust Co., CN = DST Root CA X3 --- ``` It is using the longer trust path (that allows older Android systems access). If you don't need to service any such systems, you can switch to the shorter, and newer, chain in one of two ways: [presuming you are using a relatively new version of `certbot`] - reissuing a cert with the added parameter `--preferred-chain "ISRG Root X1"` [which should them be saved and used during subsequent renewals] - manually modify the current `fullchain.pem` file; removing the last cert ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 11:59am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/5 "2021-10-02T11:59:31Z")
I do need to service older Android systems, but now they cannot connect, and I'm trying to solve it. ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 12:05pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/6 "2021-10-02T12:05:12Z")
> [@bazar](#): > > but now they cannot connect Is that now now OR just now OR the now before now? [![](https://global.discourse-cdn.com/letsencrypt/original/3X/4/c/4c9f7f2d326fe6d75b4e31065ddbdf9b0f97beba.jpeg "Spaceballs (5/11) Movie CLIP - We're in Now Now (1987) HD") ](https://www.youtube.com/watch?v=nRGCZh5A8T4) **Have you changed anything?** ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 12:06pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/7 "2021-10-02T12:06:02Z")
Since September 30 2021. ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 12:12pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/8 "2021-10-02T12:12:14Z")
There must be something wrong with your Andoid devices. Using Android 4.4.2, I can connect to: [https://api.simlr.net/](https://api.simlr.net/) It says: # 400 Bad Request But it connects without a certificate issue. ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 12:19pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/9 "2021-10-02T12:19:50Z")
On an Android 5 device, I can open this link via a browser, but the Flutter app cannot connect to this address, though it could connect before September 30. ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 12:26pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/10 "2021-10-02T12:26:01Z")
@bazar Are you sure the flutter app connects to the same port 443? I don't see any related issues at: [Issues · flutter/flutter · GitHub](https://github.com/flutter/flutter/issues) ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 12:38pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/11 "2021-10-02T12:38:12Z")
> [@rg305](#): > > Are you sure the flutter app connects to the same port 443? Definitely. ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 12:41pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/12 "2021-10-02T12:41:14Z")
@bazar Then the (client) app definitely must bring along it's own _way_ to connect (dlls, etc.) Which are incompatible with the cert being served. Other than the Flutter client app, do any other Androids connect to that same point ([https://api.simlr.net/](https://api.simlr.net/))? ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 12:44pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/13 "2021-10-02T12:44:41Z")
> [@rg305](#): > > Other than the Flutter client app, do any other Androids connect to that same point Nope, only the Flutter app. ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 12:51pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/14 "2021-10-02T12:51:38Z")
Great. Let's make them all work! Please show the web vhost config file for: `api.simlr.net:443` ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 1:02pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/15 "2021-10-02T13:02:04Z")
532 posts were merged into an existing topic: [Help thread for DST Root CA X3 expiration (September 2021)](https://community.letsencrypt.org/t/help-thread-for-dst-root-ca-x3-expiration-september-2021/149190/683) ---
**Author:** ![system](https://global.discourse-cdn.com/letsencrypt/original/3X/c/a/ca6c06ea1ea201324bba7048c6841ce60236468d.png) [@system](https://community.letsencrypt.org/u/system)\ **Post date:** [October 2, 2021, 12:54pm UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/547 "2021-10-02T12:54:35Z")
This topic was automatically closed 30 days after the last reply. New replies are no longer allowed. ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 11:05am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/548 "2021-10-02T11:05:09Z")
Hello everyone! If I understand correctly, Android \>= 2.3.6 should still work thanks to cross-sign? But my Flutter app cannot connect on Android versions prior 7.1.1 since Sep. 30. Says that certificate has expired. Lots of messages there, but still unclear what can be done on the server to continue support old (but newer than 2.3.6) Android clients. I'm running an Ubuntu server with certbot. I already told users to update Android, but this option is not always available. It should be possible to solve this issue server-side. ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 11:12am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/549 "2021-10-02T11:12:41Z")
> [@bazar](#): > > my Flutter app cannot connect How was the Flutter app TLS enabled? Which `certbot` files does it now use? ---
**Author:** ![bazar](https://avatars.discourse-cdn.com/v4/letter/b/ea5d25/32.png) [@bazar](https://community.letsencrypt.org/u/bazar)\ **Post date:** [October 2, 2021, 11:36am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/550 "2021-10-02T11:36:00Z")
The app uses dart [HttpClient](https://api.dart.dev/stable/2.14.3/dart-io/HttpClient-class.html) class. The docs say that HTTPS will work automatically _if the server's certificate is signed by a root CA (certificate authority) on the default list of well-known trusted CAs, compiled by Mozilla_. Is it the case? I didn't understant your second question about certbot files. Could you elaborate? ---
**Author:** ![rg305](https://sea3.discourse-cdn.com/letsencrypt/user_avatar/community.letsencrypt.org/rg305/32/91314_2.png) [@rg305](https://community.letsencrypt.org/u/rg305)\ **Post date:** [October 2, 2021, 11:40am UTC](https://community.letsencrypt.org/t/ubuntu-android-problem/161674/551 "2021-10-02T11:40:47Z")
> [@bazar](#): > > The docs say that HTTPS will work automatically _if the server's certificate is signed by a root CA (certificate authority) on the default list of well-known trusted CAs, compiled by Mozilla_ . Is it the case? Well that likely depends on which version of Mozilla trusted root store you are using. If it is relatively new, then I suppose, yes. > [@bazar](#): > > I didn't understant your second question about certbot files. Could you elaborate? Which ACME client are you using to get certs? Which of those files does Flutter use to encrypt with? [Next page](https://community.letsencrypt.org/t/ubuntu-android-problem/161674.md?page=2)