When using servers that are on an intranet or set up "in the cloud", such as on EC2, it is often the case that the hostname and IP number of the machine, internal to itself, is different from the hostname and IP number used to reach services on the machine from outside.

TiddlyWeb uses hostname and port number information to handle the creation of ~URLs in redirects and information used in the dynamically generated TiddlyWiki files for enabling save back to the server. To set these things adjust the server_host config setting in tiddlywebconfig.py.

When you do this on a machine with different internal and external hostnames, you need to use the external hostname, however you may see errors such as

because the external hostname or IP number is not valid for the local interface. To get around this you need to add the external hostname as an alias for the local host. On Unix-like machines this means adding to /etc/hosts.