The Sp has one and only one serial port (most other devices have two). If you connect a serial cable to the device and the other end of the serial cable to your PC running a terminal emulator such as hyperterm you should get some output, known as dialog. The dialog should, among other things tell you what version of NET+OS is running.
By default the only program running on any NET+OS-enabled device is FTP. This is the application that is programmed by manufacturing. So you should be able to ftp xxx.xxx.xxx.xxx, where xxx.xxx.xxx.xxx is the ip address of the device. NO the issue will be getting the username and password correct to be able access the device. You can try (in the form of username/password) root/password, user/password, Netsilicon/sysadm. These are username/password combinations that come to mind at this time.
I should warn you that without a NET+OS development kit, you will not be able to do too much with this device.