Installation guide

5: Interfacing with the SRA
DC 900-1325I 75
Since separate data packets in the TCP/IP stream may get sent as a single TCP/IP trans-
mission, you would need to design your own TCP/IP packet format in order for the SRA
and client program to be able to read the data correctly. A simple packet design example
is shown below:
Where the fields of the packet could be as follows:
• token (32-bit) - Any unique 32-bit pattern that would be recognizable as the start
of a packet (such as 0xABCDEF01).
• length (32-bit) - The length (in bytes) of the remainder of the packet.
• command (32-bit) - A number representing a certain command (such as start
link, stop link, data, etc.).
• data (variable) - Data sent or received on the serial line. May also be used for addi-
tional information for certain commands.
When the SRA receives data on the socket, it would first check the token to be sure that
it is indeed the start of a packet. Then it would check the length field to find out how
long the rest of the packet is. Finally, it would check the command field to determine
what action to take on the packet.
5.3 NFS Mount
You can exchange files between a client system and your SRA without having to design
an API by using the Network File System (NFS). NFS allows the Freeway server to share
directories and files with other systems over a network. By using NFS, users and pro-
grams can access files on remote client systems as if they were local files.
token length
command data