I have a Pi 3B that until today was working fine on the local network, it has a fixed IP address, e.g. 192.168.0.25, and I can ping it, and I can ssh from that Pi to any other device on the network. But ssh the opposite way is not working any longer, nor is UDP which I use for OSC communication. I have several identically configured Pis, they all behave well. That particular machine was working fine all the time, and I didn't change anything to the configuration.
What could cause this?
ping 192.168.0.25 works fine, but
ssh -vvv firstname.lastname@example.org simply says
OpenSSH_7.4p1 Debian-10+deb9u1, OpenSSL 1.0.2l 25 May 2017 debug1: Reading configuration data /etc/ssh/ssh_config debug1: /etc/ssh/ssh_config line 19: Applying options for * debug2: resolving "192.168.0.25" port 22 debug2: ssh_connect_direct: needpriv 0 debug1: Connecting to 192.168.0.25 [192.168.0.25] port 22. debug1: connect to address 192.168.0.25 port 22: Connection refused ssh: connect to host 192.168.0.25 port 22: Connection refused
and Open Sound Control messages via UDP simply don't arrive any longer.
sudo service ssh status says ssh daemon is active and listening on port 22 (0.0.0.0). ifconfig confirms the IP address is set as I thought. I have no idea what's wrong now. My only idea now is to duplicate the SD image from one of the other Pis. But sure there must be an explanation.