UDP Networking

Introduction

The radar acts as a UDP client/server and therefore can send and receive UDP datagrams. The radar supports a UDP IP address that can be a multicast address and defaults to 239.69.69.69 on port 6317, which, is IANA-allocated to Navtech. The IP addresses and the port are all configurable via the radar management software.

Contents

UDP Message Structure

Each message includes a header of 8 bytes followed by a variable length payload. The header includes the message type and payload size enabling the client software to reliably decode the payload data as required. When sending messages to a radar if the Radar Serial number field is set to 0 then the message is considered a broadcast and all radar will respond. To send a message to specific radar set the serial number to that of the radar that is required to respond.

Typically there are 2 types of payloads;

• Byte array representing a structure made up from standard C++ data types

• Byte array representing a serialised Protocol Buffer message

• Byte arrays that represent both of the above

For more information on Google Protocol Buffers please see reference [Protocol Buffers ]. Navtech can provide Protobuf message files on request.

The Complete UDP Message Structure

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The UDP Message Header

This is the first part of every message sent using this protocol. The provides information about the body of the message.

UDP Message Header Structure

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UDP Message Types

The UDP Message Body

The body of the message will contain one of the message types outlined in section 2.3.2. This payload will be variable length, the size being specified in the message header. The rest of this document describes the message types.

Discovery Message

The discovery message contains the minimal information a client application needs to connect to the radar. The message provides all critical data in fixed length fields at the beginning of the message. These values are the minimum required in order to successfully connect a client to the TCP server. These fields can be accessed using the normal process of decoding a byte stream coming across the network. The remainder of the message is made up from a variable length Protocol Buffer message which contains additional information about the radar, such as serial numbers and service dates. Advanced customer applications would be expected to decode this message data however the information is optional. The size of this message body is specified by the payload size field in the header. The size of the Protocol Buffer message can be calculated by subtracting the size of the fixed length fields from the payload size (i.e. Payload Size – 22 bytes). A configuration message is always sent when a client first connects and is also sent in response to a request from the client.

Discovery Message Structure

Discovery Protocol Buffer Payload

Feature Flag layout

The Feature Flag is a 32-bit word, interpreted as a set of bitfields as shown below:

Update Network Settings

The update network settings message contains all of the information required to change the IP settings of the radar. The message provides all critical data in fixed length fields at the beginning of the message. These values are the minimum required in order to successfully configure the IP settings of the radar. These fields can be accessed using the normal process of decoding a byte stream coming across the network.

Update Network Settings Message Structure

Point Cloud Data

Point Cloud data messages are emitted by the radar if the Point Cloud output is enabled.

A point cloud data message represents one azimuth of data. The message payload consists of zero or more points, which represent a set of radar returns along the azimuth that exceed some configured threshold. The parameters for controlling the point cloud output are controlled via the Navigation Configuration Colossus TCP message.

Point Cloud Data Message Structure

Point Cloud Point Structure

Related Information