Unable to complete network request to host XYZ. Failed to locate host machine. The specified name was not found in the hosts file or Domain Name Services.

You might get this error when you try to connect to some Firebird server using the hostname:database_path syntax (i.e. XYZ:database), and it cannot find the hostname XYZ.

If you're using Delphi, and you just changed the default setting from IB_SERVER:something to IB_SERVER:something_else, you should know that IB_SERVER needs to be a valid hostname. If you're connecting to a Firebird server installed on the same machine, replace IB_SERVER with LOCALHOST and you're good to go.

Otherwise, it probably a host name resolving issue. Each hostname needs to be resolved to IP address for the connection to succeed. The hostname XYZ should either be listed in your hosts file (/etc/hosts on Linux, varies on Windows, try c:\windows\system32\drivers\etc\hosts) or defined in your DNS server. You can check the resolving using the 'ping' command:

ping XYZ

If it does not work, you have the following options:

a) Use IP address instead of hostname in the connection string

b) Edit the 'hosts' file and add the appropriate line for this host. Example:

192.168.0.22 XYZ

c) Contact your network administrator to learn why DNS resolving does not work.