Errors

There are three exception types you'll see from the library, all rooted at RhpProtocolException.

classDiagram
    Exception <|-- RhpProtocolException
    RhpProtocolException <|-- RhpServerException
    RhpProtocolException <|-- RhpTransportException

RhpServerException

Thrown when an RHP request gets a non-zero errcode/errCode reply.

try
{
    await rhp.OpenAsync(ProtocolFamily.Ax25, SocketMode.Stream,
        port: "99", local: "G8PZT", flags: OpenFlags.Passive);
}
catch (RhpServerException ex) when (ex.ErrorCode == RhpErrorCode.NoSuchPort)
{
    Console.Error.WriteLine("Radio port 99 doesn't exist on this node.");
}

The exception carries:

• int ErrorCode — the canonical numeric code (see protocol primer).
• string? ErrorText — the server's errtext, if present.
• RhpErrorCode.IsTransient(code) is a useful helper for retry logic (returns true for Unspecified, NoMemory, NoBuffers).

RhpTransportException

Thrown when the underlying TCP connection ends mid-conversation. All in-flight requests get this exception so callers don't hang forever:

try
{
    await rhp.SendOnHandleAsync(h, "data\r");
}
catch (RhpTransportException ex)
{
    Console.Error.WriteLine($"link dropped: {ex.Message}");
}

The Disconnected event also fires when this happens, carrying the underlying exception (or null for a clean EOS).

RhpProtocolException

The base class. You'll see it directly only for malformed JSON or for "reply type didn't match request" mismatches — both of which generally indicate a protocol-level bug rather than something to recover from.

Retry guidance

async Task<int> OpenWithRetry()
{
    var delay = TimeSpan.FromMilliseconds(200);
    for (int attempt = 1; ; attempt++)
    {
        try
        {
            return await rhp.OpenAsync(...);
        }
        catch (RhpServerException ex) when (RhpErrorCode.IsTransient(ex.ErrorCode) && attempt < 5)
        {
            await Task.Delay(delay);
            delay *= 2;
        }
    }
}