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RocNet ⇒ Rocrail® Network

This is an binary Open Source protocol intended for communication between two or more, in a peer to peer network, hardware units.

The idea is to build a network of two or more units of operation.
There are different types of units:

• I/O, for switches, signals, sensors, …
• DCC generators
• WLAN enabled stationary and mobile decoders
• computers
• …

All should have their own unique ID which is used as sender/recipient parameter in the header.
The unit who is processing all messages and sends a lot of them can be entitled to be the host of the network, but in fact it is only a player in the game.
So in the case of Rocrail the computer running this software could be seen as the host.

More information about setting up the RocNet connection: Setup

UDP is the default and the recommended communication method which is also used in combination with the RocNetNodes.
All other methods are restricted to "one-to-one" communication.

Default settings:

• address: 224.0.0.1 (http://en.wikipedia.org/wiki/Multicast_address#IPv4_multicast_addresses)
• port: 4321 → Make sure that no other service is running on the same port!

This can be used for serial communication using ASCII characters only.
A packet start is marked with an @ and the rest of it is HEXA¹⁾. (The value of 255 is represented in HEXA as "FF", 100 as "64" and so on…)
The used ASCII characters:

@ 0 1 2 3 4 5 6 7 8 9 A B C D E F

After detecting the start of a packet the first 16 character (8 bytes), the header, can be read.
The data length is in the last two characters of the header. In this case the length must be multiplied by two to read the data part.

Example:
A track power on command send from the server:

@000000000101020101

The netid byte must have bit 7, 0x80, set hight to signal the start of the packet. All other byte may only use 7 bit, 0x7F, data load.

Default settings:

• device: com1

  <digint iid="rn-1" lib="rocnet" sublib="serial" device="com1" bps="19200">
    <rocnet id="1" crc="true"/>
  </digint>

To group units in a large system. Leave zero if there is only one active network.
Bit 7 must be set in case of 7 bit serial.
Alternatively it can be used as location ID for logically grouping nodes in an overview dialog.

Every unit in the network has its own ID.
If left to zero all units must evaluate the packet. This can be of use for queries to see which devices are available.

The ID of the sender unit. Rocrail Server default ID is 1.
A value of "0" is for broadcasting.

If the action needs an address it will be provided in the first two bytes of data part. (Extended format)

Netto number of following data bytes.

The variable part of the packet which is action dependent.
The length may be set to zero if no further information is needed for the given action.

ID zero is for all networks.

8 bit ID = idL + idH * 256

7 bit ID = idL + idH * 128

• 0 request
• 1 event
• 2 reply

If the type is an event or reply, no real I/O action should be taken on the specified address; mostly the I/O with this address signals a state change.

Optional for 7-bit serial connections:
The 1's complement of the byte wise Exclusive OR of all the bytes in the message.

unsigned char rnChecksum(const unsigned char *b, int len) {
  unsigned char chksum = 0xff;
  int i;
  for (i = 0; i < len; i++) {
    chksum ^= b[i];
  }
  return chksum;
}

Binary representation:

00 00 00 00 01 02 02 03 00 00 00

ASCII HEXA representation:

@0000000001020203000000

Direction and lights are left unchanged because bit 6 of both bytes are not set.

• Loco address = 291
• Velocity = 48
• Direction = forwards
• Lights = off

Binary representation:

00 01 23 00 01 02 02 03 30 41 40

ASCII HEXA representation:

@0001230001020203304140

¹) All connected stationary decoders should report status if recipient is set to zero.
²) The push button on the node will trigger the RocNetNode dialog to popup with the node selected. A show request from the host will flash the LED on the node.

For programming stationary decoders the address represents the module address.

The read, write and delete port/channel may contain up to 8 port configurations.
The read and write macro may contain up to 8 commands.

The Input Group is not used and not defined; Use the Sensor group.

¹) Address of the reporting loco.
The sensor ID is set in the header; Sender.
A sensor secure ack is done with the stationary acknowledge message:

• Code = 1
• Port = port

• rocnet-const.h.zip Header file for C.