Faactory.Channels.JT808 0.6.1

Channels - JT/T 808 Protocol

This project contains a set of Channels adapters to decode data encoded with JT/T 808 protocol.

Learn more about Channels.

Getting started

Install the package from NuGet

dotnet add package Faactory.Channels.JT808

To enable decoding of JT808 packets on the input pipeline, we just need to register the respective middleware with the channel pipeline. We do that with an extension method.

IChannelBuilder builder = ...;

builder.AddJT808Middleware();

With the middleware registered, implement your own middleware to handle the decoded messages.

Generally, if there's a specific reader in place, messages are delivered as a Message<T> where T is the model for the specific data.

Unsupported or unknown JT/T 808 message types are forwarded as BinaryMessage, allowing custom adapters or handlers to process proprietary extensions or non-implemented messages.

After decoding, the middleware emits the following message types:

• Message<GeneralResponse>
• Message<TerminalRegistration>
• Message<TerminalAuthentication>
• Message<TerminalLogout>
• Message<TerminalAttributeResponse>
• Message<TerminalParameterResponse>
• Message<LocationInformation>
• Message<LocationInformationQueryResponse>
• Message<BatchLocationInformation>
• Message<UplinkPassthroughData>

Sending Messages

To send a message to the device, the easiest (and recommended) way is to make use of the IMessageBuilder interface. To obtain an instance, call the GetMessageBuilder() extension method on IChannel or IChannelContext.

public class MyHandler : ChannelHandler<Message<TerminalAuthentication>>
{
    // ...

    public override async Task ExecuteAsync( IChannelContext context, Message<TerminalAuthentication> message )
    {
        // ...

        EncodedMessage acknowledge = context.GetMessageBuilder()
            .Platform.Response( message, OperationResult.Success );

        context.Output.Write( acknowledge.Buffer );

        // ...
    }
}

Message Encapsulation

If a message is encapsulated (split across multiple packages), decoding is deferred until all packages are received. An internal encapsulation service reassembles the packages and pushes a single reconstructed message into the pipeline.

DateTime and Timezones

The JT/T 808 protocol does not specify a default timezone for the dates and times. It also does not specify the timezone of the data sent by the device. This means, unfortunately, that the timestamps cannot be interpreted correctly unless the device timezone is known beforehand.

For this reason, the library decodes the dates and times with an unspecified timezone. It is up to the implementer to determine the correct timezone of the device and convert them accordingly.