CC can't connect from some networks. Other apps/browser connect work. Please help.

TheRealJohnAdams · 07-12-2024, 08:01 AM

I have Calibre running in a docker container on my NAS. I use SWAG (nginx proxy plus some extras) to access Calibre from my domain name. I should be able to access Calibre anywhere with an internet connection, and I mostly can:

From any network with a connection, I can go to calibre.mydomain.me/content-server/, and it works as expected.
From any network with a connection, I can use Calibre Sync to connect to my Calibre server, and it works as expected.
From some networks (including my home network, Starbucks wifi, my parents' home wifi, etc.), I can use Calibre Companion to connect to my Calibre server, and it works as expected.
From other networks (including my phone hotspot and my aunt's home wifi), I get the "Cannot find Content Server" error when I try to connect.

I am not sure where to begin troubleshooting this. The fact that it happens on some networks but not others suggests that it is a network configuration issue. But the fact that it happens with Calibre Companion and not with other apps suggests that it is a problem with Calibre Companion. Any suggestions?

Note: I realize that Calibre Companion has been abandoned. I downloaded the last working version of the APK and signed it to prevent updates. If this bug could be resolved, the existing version of Calibre Companion would meet all of my needs.

TheRealJohnAdams · 07-15-2024, 10:46 AM

Update: I have not been able to solve the problem. However, I was able to find a workaround. Using a VPN to connect to my home network allows Calibre Companion to work normally. This is not optimal but it is good enough.

fonbon · Today, 07:55 AM

Given the specific issue you’re encountering with Calibre Companion being unable to connect to the Calibre server from certain networks, it seems like the problem is multifaceted, involving both network configurations and the app itself. Here are some steps you can take to troubleshoot and potentially resolve this issue:

1. Check DNS Resolution
On the networks where Calibre Companion is failing to connect, ensure that DNS resolution is working correctly for your domain (calibre.mydomain.me). You can do this by:

Opening a terminal or command prompt.
Running ping calibre.mydomain.me to see if it resolves to the correct IP address.
Running nslookup calibre.mydomain.me to check if the DNS server resolves the domain properly.
2. Firewall and Network Configuration
Some networks might have firewall rules or network configurations that block specific types of traffic or ports. Ensure that:

Port 8080 (or the port your Calibre server is running on) is open and not blocked by the network's firewall.
The router or firewall settings on networks where it fails aren’t blocking the traffic required for Calibre Companion to connect.
3. SSL/TLS Configuration
Since you are using SWAG (Secure Web Application Gateway) which likely involves SSL/TLS:

Ensure that the SSL certificates are correctly installed and not expired.
Verify that all intermediate certificates are correctly configured.
4. Proxy Settings
Check if the networks where it fails have proxy settings that might be interfering:

Some networks might require specific proxy settings to access external services.
Check if there are any network-specific proxy configurations on the networks where Calibre Companion fails.
5. App Configuration
Since Calibre Companion is an older app and has been abandoned, it might have issues with certain modern network configurations:

Double-check the server address and port configuration in Calibre Companion.
Try using the IP address directly instead of the domain name in Calibre Companion to rule out DNS issues.
6. Logs and Debugging
Check the logs for both SWAG and the Calibre server for any errors or connection attempts:

Look for any errors or warnings in the SWAG (Nginx) logs that might indicate why the connection is being blocked or dropped.
Check the Calibre server logs to see if there are any failed connection attempts from the networks where it doesn’t work.
7. Mobile Network Restrictions
For mobile networks (like your phone hotspot), there may be additional restrictions:

Some mobile carriers block certain types of traffic or have NAT configurations that could interfere with Calibre Companion.
Try enabling a VPN on your mobile device to see if it resolves the issue.
8. Alternative Apps
Since Calibre Companion has been abandoned, consider using an alternative app like Calibre Sync, which you mentioned works on all networks. This might involve changing your workflow slightly but could provide a more consistent experience across different networks.

Summary
To narrow down the issue, start by ensuring that DNS resolution and firewall settings are consistent across the networks where it fails. Pay close attention to network-specific configurations and consider using a VPN to bypass potential restrictions. Since Calibre Companion is outdated, exploring alternative apps that are actively maintained might ultimately provide a more reliable solution.

07-12-2024, 08:01 AM	#1
TheRealJohnAdams Enthusiast Posts: 41 Karma: 57668 Join Date: May 2020 Device: Kindle Oasis, Kobo Forma, Onyx Page	CC can't connect from some networks. Other apps/browser connect work. Please help. I have Calibre running in a docker container on my NAS. I use SWAG (nginx proxy plus some extras) to access Calibre from my domain name. I should be able to access Calibre anywhere with an internet connection, and I mostly can: From any network with a connection, I can go to calibre.mydomain.me/content-server/, and it works as expected. From any network with a connection, I can use Calibre Sync to connect to my Calibre server, and it works as expected. From some networks (including my home network, Starbucks wifi, my parents' home wifi, etc.), I can use Calibre Companion to connect to my Calibre server, and it works as expected. From other networks (including my phone hotspot and my aunt's home wifi), I get the "Cannot find Content Server" error when I try to connect. I am not sure where to begin troubleshooting this. The fact that it happens on some networks but not others suggests that it is a network configuration issue. But the fact that it happens with Calibre Companion and not with other apps suggests that it is a problem with Calibre Companion. Any suggestions? Note: I realize that Calibre Companion has been abandoned. I downloaded the last working version of the APK and signed it to prevent updates. If this bug could be resolved, the existing version of Calibre Companion would meet all of my needs.

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07-15-2024, 10:46 AM	#2
TheRealJohnAdams Enthusiast Posts: 41 Karma: 57668 Join Date: May 2020 Device: Kindle Oasis, Kobo Forma, Onyx Page	Update: I have not been able to solve the problem. However, I was able to find a workaround. Using a VPN to connect to my home network allows Calibre Companion to work normally. This is not optimal but it is good enough.

Today, 07:55 AM	#3
fonbon Junior Member Posts: 1 Karma: 10 Join Date: Jul 2024 Device: nobe	Given the specific issue you’re encountering with Calibre Companion being unable to connect to the Calibre server from certain networks, it seems like the problem is multifaceted, involving both network configurations and the app itself. Here are some steps you can take to troubleshoot and potentially resolve this issue: 1. Check DNS Resolution On the networks where Calibre Companion is failing to connect, ensure that DNS resolution is working correctly for your domain (calibre.mydomain.me). You can do this by: Opening a terminal or command prompt. Running ping calibre.mydomain.me to see if it resolves to the correct IP address. Running nslookup calibre.mydomain.me to check if the DNS server resolves the domain properly. 2. Firewall and Network Configuration Some networks might have firewall rules or network configurations that block specific types of traffic or ports. Ensure that: Port 8080 (or the port your Calibre server is running on) is open and not blocked by the network's firewall. The router or firewall settings on networks where it fails aren’t blocking the traffic required for Calibre Companion to connect. 3. SSL/TLS Configuration Since you are using SWAG (Secure Web Application Gateway) which likely involves SSL/TLS: Ensure that the SSL certificates are correctly installed and not expired. Verify that all intermediate certificates are correctly configured. 4. Proxy Settings Check if the networks where it fails have proxy settings that might be interfering: Some networks might require specific proxy settings to access external services. Check if there are any network-specific proxy configurations on the networks where Calibre Companion fails. 5. App Configuration Since Calibre Companion is an older app and has been abandoned, it might have issues with certain modern network configurations: Double-check the server address and port configuration in Calibre Companion. Try using the IP address directly instead of the domain name in Calibre Companion to rule out DNS issues. 6. Logs and Debugging Check the logs for both SWAG and the Calibre server for any errors or connection attempts: Look for any errors or warnings in the SWAG (Nginx) logs that might indicate why the connection is being blocked or dropped. Check the Calibre server logs to see if there are any failed connection attempts from the networks where it doesn’t work. 7. Mobile Network Restrictions For mobile networks (like your phone hotspot), there may be additional restrictions: Some mobile carriers block certain types of traffic or have NAT configurations that could interfere with Calibre Companion. Try enabling a VPN on your mobile device to see if it resolves the issue. 8. Alternative Apps Since Calibre Companion has been abandoned, consider using an alternative app like Calibre Sync, which you mentioned works on all networks. This might involve changing your workflow slightly but could provide a more consistent experience across different networks. Summary To narrow down the issue, start by ensuring that DNS resolution and firewall settings are consistent across the networks where it fails. Pay close attention to network-specific configurations and consider using a VPN to bypass potential restrictions. Since Calibre Companion is outdated, exploring alternative apps that are actively maintained might ultimately provide a more reliable solution.