Can connect to 'ServerName' but not to its IP address

I'm using SQL Manager from my Enterprise server to connect to my SQL Express server that will act as a witness to a db mirroring system. If I try to connect to the SQL Express server using its IP address, I get a "named pipes error 53." If I connect by browsing the network and connect to the Name of the Server "Machinename\SQLExpress", I am successful. I would like to be able to connect to the IP directly as it's not dependant upon certain services to be started or configured a certain way.

Thank you,

ChadTry Data Source=tcp:192.168.0.3,1433 in your connection string using applicable IP and port number (remember to setup port number in SQL Configuration Manager on the SQL Express machine).