Pamoja.Coap 0.2.0

Pamoja.Coap

A CoAP client and the server it reports to, over UDP, with confirmable delivery and observe. One capability of pamoja, one memory-safe Rust core with bindings for TypeScript, Python, and C#.

Install

dotnet add package Pamoja.Coap

using Pamoja.Coap;

This pulls in Pamoja.Native, the compiled engine, and Pamoja.Core. dotnet add package Pamoja is the whole framework in one package.

Example

The guide project's example, spliced here as it ran in CI.

From bindings/dotnet/samples/Pamoja.Guides/CoapGuide.cs:

// The gateway in the orchard's shed. It takes moisture readings from every row,
// and holds the irrigation valve's state for the rows to observe. Port 0 lets the
// system pick a free port, which the rows are pointed at below.
using var gateway = new CoapServer("127.0.0.1:0");
await gateway.ConnectAsync();
await gateway.SubscribeAsync("orchard/+/moisture");
await gateway.SendAsync("orchard/valve", "closed");
ushort port = gateway.LocalPort!.Value;
Console.WriteLine("gateway   takes moisture readings on orchard/+/moisture");

// A battery-powered sensor in row 7. Its reading is confirmable, so it waits for
// the gateway's acknowledgment and retransmits until one comes back.
using var row7 = new CoapClient(new CoapClientOptions
{
    Host = "127.0.0.1",
    Port = port,
    AckTimeoutMs = 200,
});
await row7.ConnectAsync();
await row7.SendAsync("orchard/row-7/moisture", "31");
Console.WriteLine("row-7     reported 31, and the gateway acknowledged it");
TransportMessage reading = (await gateway.ReceiveAsync())!;
Console.WriteLine($"gateway   took {reading.Text} from {reading.Topic}");

// Observing the valve registers the row with the gateway, which answers with the
// valve's state now and notifies every change after it, as RFC 7641 describes.
await row7.SubscribeAsync("orchard/valve");
TransportMessage current = (await row7.ReceiveAsync())!;
Console.WriteLine($"row-7     observes {current.Topic}, which reads {current.Text}");
await gateway.SendAsync("orchard/valve", "open");
int observers = gateway.Observers("orchard/valve");
Console.WriteLine($"gateway   opened the valve for {observers} observer");
TransportMessage change = (await row7.ReceiveAsync())!;
Console.WriteLine($"row-7     {change.Topic} now reads {change.Text}");

// A path the gateway does not take is answered 4.04, and a confirmable send
// reports that rather than counting the reading as delivered.
try
{
    await row7.SendAsync("orchard/row-7/battery", "3.1");
    Console.WriteLine("row-7     the battery reading was taken, which should never happen");
}
catch (PamojaException error)
{
    Console.WriteLine($"row-7     battery refused: {error.Message}");
}

// Row 8 sends non-confirmable: once and unacknowledged, which costs the least
// radio time and suits a reading whose loss costs nothing.
using var row8 = new CoapClient(new CoapClientOptions
{
    Host = "127.0.0.1",
    Port = port,
    Reliability = Reliability.NonConfirmable,
});
await row8.ConnectAsync();
await row8.SendAsync("orchard/row-8/moisture", "27");
Console.WriteLine("row-8     sent 27 without waiting for an answer");
TransportMessage unconfirmed = (await gateway.ReceiveAsync())!;
Console.WriteLine($"gateway   took {unconfirmed.Text} from {unconfirmed.Topic}");

// Row 9 is pointed at port 1, where nothing listens. A confirmable send
// retransmits on a doubling wait and then gives up. RFC 7252's defaults would take
// more than a minute to get there, so this one waits 20 ms and retransmits once.
using var row9 = new CoapClient(new CoapClientOptions
{
    Host = "127.0.0.1",
    Port = 1,
    AckTimeoutMs = 20,
    MaxRetransmits = 1,
});
await row9.ConnectAsync();
try
{
    await row9.SendAsync("orchard/row-9/moisture", "29");
    Console.WriteLine("row-9     an empty port acknowledged it, which should never happen");
}
catch (PamojaException error)
{
    Console.WriteLine($"row-9     gave up unacknowledged: {error.Message}");
}

The same capability in every language

Documentation

• Pamoja.Coap reference, every type in this namespace.
• The CoAP guide, with the same example in Rust, TypeScript, and Python.
• Every capability, and the install page.

License

MIT