Default ports for SQL Backup software are 6000 for SQL Backup Agent and 6001 for SQL Storage Server ,both ports are TCP port . Please make sure these ports are not blocked by firewall. If these ports are used by another program , you can change them in Backup Agent Manager and Storage Server Manager .
(After change ports ,you have to restart service in first tab "Service")
(Start -> All Programs -> SQL Server Backup x -> Backup Agent -> Backup Agent Manager)
(Start -> All Programs -> SQL Server Backup x -> Storage Server -> Storage Server Manager)
For more detail about SQL Server Backup Software Architectural , please visit here :