To use my domain name programmatically doesn't work any more

I created my domain name on amazon and it worked before with my old instance. I then followed the described procedure to reattach it to the new instance. And if I enter the domain name in a brower it works. It works also programmatically with https but very slowly as described. It doesn't work as part of jdbc url with which I try to connect to the database though. I don't understand what you mean by localhost file, I locally use a mac and it has a .ssh/known_hosts file which I updated

I have now checked the https log more thourougly and found the following: DEBUG [2024-01-10 16:56:51.051] [Worker-9: https://guenthermahr.com/languageTrainer/updateVokDev/plugins/VocabularyTrainerRCP_1.0.0.202401101541.jar] org.apache.hc.client5.http.ssl.SSLConnectionSocketFactory - Starting handshake DEBUG [2024-01-10 16:56:51.051] [Worker-11: https://guenthermahr.com/languageTrainer/updateVokDev/plugins/VocabularyUtil_1.0.0.202401101541.jar] org.apache.hc.client5.http.impl.io.DefaultHttpClientConnectionOperator - http-outgoing-19 connect to guenthermahr.com/52.59.75.197:443 timed out. Connection will be retried using another IP address DEBUG [2024-01-10 16:56:51.051] [Worker-11: https://guenthermahr.com/languageTrainer/updateVokDev/plugins/VocabularyUtil_1.0.0.202401101541.jar] org.apache.hc.client5.http.impl.io.DefaultHttpClientConnectionOperator - http-outgoing-19 connecting to guenthermahr.com/18.158.19.149:443 DEBUG [2024-01-10 16:56:51.051] [Worker-11: https://guenthermahr.com/languageTrainer/updateVokDev/plugins/VocabularyUtil_1.0.0.202401101541.jar] org.apache.hc.client5.http.ssl.SSLConnectionSocketFactory - Connecting socket to guenthermahr.com/18.158.19.149:443 with timeout 120000 MILLISECONDS DEBUG [2024-01-10 16:56:51.051] [Worker-9: https://guenthermahr.com/languageTrainer/updateVokDev/plugins/VocabularyTrainerRCP_1.0.0.202401101541.jar] org.apache.hc.client5.http.ssl.SSLConnectionSocketFactory - Secure session established

The 1st ip is wrong, the 2nd correct

Now I found it: under Lightsail/DNS records the second ip (first in my last post) still existed: I think it was the dynamic ip after creation which I thought was deleted when I attached the static address to it. Both ips were attached to my domain name and so the program obviously didn't know which one to take and tried the wrong one first and only after that the second. It worked with https, but not with the database which ran into a timeout. After deletion of the wrong ip everything is fine now.

In the specific case of the database when I use the domain name I run into a timeout: there's no log on the db server itself as it is obviously not reached. So it's just (as this is Java) a jdbc timeout message.

In the case of https, there is also no specific message: actually the functionality works (in this case I use the domain name!), but it works very slowly as I said (the program contacts an update site to look for updates, which it then, if found, imports).

Thank you for your answer. There is no firewall. But as explained in my last post, the problem is already solved. It was due to the fact that the original dynamic ip address was still pointing to my site after I reattached the static ip address from the old instance. I didn't know that I had to explicitly delete that dynamic address. Both addresses were attached to my domain, but only the static ip address was valid and that caused the trouble.