Skip to content

Latest commit

 

History

History
55 lines (35 loc) · 2.67 KB

ext000d-wrapped-packet.md

File metadata and controls

55 lines (35 loc) · 2.67 KB

EXT000D: Wrapped Packet

  • Extension dependencies: no
  • Document status: Approved on 2020-02-01

This extension allows you to wrap a packet with any data in the Overvis Connect protocol packet.

Wrapped packets in length can exceed the Overvis Connect packet length limit set for this session, and they are split and transmitted by several commands in a row (see below). In fact, it allows you to tunnel any protocol (HTTP, FTP, etc.).

Commands (CMD)

0017 Exchange Wrapped Packets

This command serves as a wrapper for exchanging binary data in any format.

If the request does not fit into one packet, then it is sent by several commands in a row, while the device responds only with the OFFSET field, without data, to all commands except the last one. If the device cannot process a request of the specified length, it will return an error in response to any of the commands that send a long request.

If the response does not fit into one packet, then it is required to send several commands with the OFFSET field, without data, to the device to receive all parts of the response.

Request

<TID> 3900 <LEN> 0017 <OFFSET> [ <REMLEN> <BLOCKDATA> ]

Fields

Field Length (bytes) Description
OFFSET 4 Block offset in the request, if there are REMLEN and BLOCKDATA fields. Otherwise, match the value of OFFSET + BLOCKDATA of the previous received response to get the next part.
REMLEN 4 Remaining request length in bytes. The total length of the request is equal to the sum of the length of BLOCKDATA and the fields OFFSET and REMLEN. If REMLEN is 0, then this is the last part of the request.
BLOCKDATA LEN - 10 Request data block.

Response

<TID> 3900 <LEN> 0017 <OFFSET> [ <ESTREM> <BLOCKDATA> ]

Fields

Field Length (bytes) Description
OFFSET 4 Block offset in response, if there is a BLOCKDATA field. Otherwise, it is the same as the value OFFSET + BLOCKDATA of the request, which confirms the receipt of a part of the request and expectation of the next part.
ESTREM 4 An estimate of the remaining length of the response in bytes. The estimate of the total length of the response is equal to the sum of the length of BLOCKDATA plus the fields OFFSET and ESTREM. If ESTREM is 0, then this is the last part of the answer.
BLOCKDATA LEN - 10 Response data block.

Errors

Code Description
0010 The total length of the request is too long.
0011 Invalid OFFSET value.