Communications with the NetLoader is effected by sending programming commands as UDP datagrams to port 65535 of the DS. For each command the NetLoader sends a reply, also in the form of a UDP datagram. Reply to a particular command is always sent to the IP-address and the port number from which this command was received.
Because each command and reply is sent in its own UDP datagram no additional encapsulation is necessary.
All NetLoader commands have the following format:
|•||C.C. is the command code. Command code always consists of a single ASCII character. All available commands and their codes are listed in the command table at available commands.|
|•||Optional parameter(s) field contains necessary data if required by the command.|
All NetLoader replies have the following format:
|•||R.C. is the reply code. Reply codes always consist of a single ASCII character and inform the sender of the command about the result of command execution.|
|•||Optional Data field contains necessary data (if any).|
Example: here is a sample exchange between the network host and the DS running NetLoader. Each line represents the data in a separate UDP datagram.
DS(NetLoader)-->Host: A<NV1.10 Netloader>
This method of exchanging commands and replies is exactly the same as the one used by the application firmware of the DS where it is called out-of-band (UDP) programming . UDP communications with the application firmware and the NetLoader are the same except for the following small differences:
|•||Latest versions of the application firmware accept UDP commands on two ports- 65535 and 32767. The NetLoader can only accept UDP commands on port 32767.|
|•||To speed up command execution the application firmware accepts multiple UDP commands (this is based on using additional command ID field). The NetLoader doesn't supports this feature and all commands should be sent strictly one-by-one i.e. the network host should not intentionally send the next command without first receiving (waiting for) a reply to the previous command.|
Except for the above two differences UDP communications with the NetLoader is the same as UDP communications with the application firmware. Just like the application firmware, the NetLoader supports broadcadt UDP programming , which is initiated by the Select In Broadcast Mode (W) command . There are other commands that have similar or identical "parallel" commands in the application firmware- Echo (X) command , Verify and Start Firmware (E) command , Get Firmware Version (V) command .
UDP programming is called (in the Application Firmware Manual ) out-of-band (UDP) programming because there is also inband (TCP) programming that relies on TCP communications with the DS. Because of size constraints the NetLoader doesn't support TCP communications and the only available method of exchanging commands and replies is the one based on UDP commands.