Local Protocol

Pia > Protocols > Station Protocol

This protocol is used in LDN mode. Unless specified otherwise, the messages in this protocol are encoded with little endian byte order.

Message Type	Description
0x11	Update session
0x12	Destroy network
0x13	Start host migration
0x21	Update session ack

The following version number is advertised during the connection request:

Pia version	Version
5.19 - 5.45	0

Local message header

5.2 - 5.45:

Offset	Size	Description
0x0	1	Version number (1)
0x1	1	Message type
0x2	2	Payload size
0x4	6	Always 0
0xA	2	Padding

Update session message

This message is sent by the host of the network whenever a station joins, leaves, or when the allow participation state is changed. It is resent every 100 milliseconds until all stations in the network have acknowledged the message.

The sequence id starts at a random value and is incremented whenever the network changes.

The network id is a random value that is generated once when the network is created. It is not the same as the network id that is broadcast in the application data.

5.2:

Offset	Size	Description
0x0	12	Local message header
0xC	4	Sequence id
0x10	4	Network id (random)
0x14	4	Host variable id
0x18	1	Allow participation
0x19	7	Padding
0x20		Payload

5.7 - 5.45:

Offset	Size	Description
0x0	12	Local message header
0xC	4	Sequence id
0x10	4	Network id (random)
0x14	4	Host variable id
0x18	4	Host service variable id
0x1C	4	Padding
0x20	8	Host constant id
0x28	1	Allow participating state
0x29	7	Padding
0x30		Payload

Update session payload

5.2 - 5.45:

Offset	Size	Description
0x0	8 x 9	Local nodes
0x48	1	Host migration state

Destroy network message

5.9:

Offset	Size	Description
0x0	12	Local message header
0xC	4	Always 0

Start host migration message

5.9:

Offset	Size	Description
0x0	12	Local message header
0xC	4	Always 0

Ack message

5.9 - 5.45:

Offset	Size	Description
0x0	12	Local message header
0xC	4	Sequence id
0x10	4	Always 0

Local node

5.2 - 5.45:

Offset	Size	Description
0x0	8	Local address
0x8	1	Host migration ranking

The oldest node in a network has host migration ranking 0. The next oldest node in the network has host migration ranking 1, and so on.

The host migration ranking seems to be update only when a new node joins the network, but not when a node leaves the network.

For unused entries in the list, the host migration ranking is set to 255, and the local address is cleared with zeros.

Local address

Unlike the rest of the messages, a local address is encoded with big endian byte order.

5.2 - 5.45:

Offset	Size	Description
0x0	6	Inet address (IPv4)
0x6	2	Extension address (always 0)