The 884XA meters actually don't have a user password. So why is it asking for one? This is a protection Telnet and other relatively generic LAN communication applications use to eliminate unauthorized connections.
However, if you use a Raw socket connection and the default port address you will not be asked for a password.
Setting up your communication this way (Here is an example using PuTTY), will automatically look at the connection on the port and bypass the need for a password. You may also have to allow the port access through your firewall.