Joseph Doherty
47 lines
2.3 KiB
C#
47 lines
2.3 KiB
C#
namespace ZB.MOM.WW.OtOpcUa.Driver.Modbus;
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/// <summary>
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/// Raised when a Modbus TCP transaction leaves the single-flight socket in an unknown /
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/// desynchronized state — a per-op response timeout, or a framing violation (transaction-id
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/// mismatch or truncated MBAP length). Unlike a Modbus <em>exception PDU</em> (a well-formed
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/// protocol-level error where the socket is still coherent and the request must simply
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/// propagate), a desync means bytes may still be in flight or half-read, so the socket is
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/// unusable and MUST be torn down before this is thrown.
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/// </summary>
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/// <remarks>
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/// Derives from <see cref="IOException"/> deliberately: the transport's existing
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/// reconnect-and-retry classifier (<c>IsSocketLevelFailure</c>) already treats
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/// <see cref="IOException"/> as socket-fatal, so with auto-reconnect enabled the transport
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/// transparently reconnects and resends once; with auto-reconnect disabled the (already torn
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/// down) socket is never reused and this surfaces to the driver's status mapping as a
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/// communication error.
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/// </remarks>
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public sealed class ModbusTransportDesyncException : IOException
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{
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/// <summary>The reason the socket was classified desynchronized.</summary>
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public enum DesyncReason
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{
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/// <summary>The per-op deadline (linked <c>CancelAfter</c>) fired — the response never arrived in time.</summary>
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Timeout,
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/// <summary>The response MBAP transaction id did not match the request's.</summary>
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TxIdMismatch,
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/// <summary>The response MBAP length field was below the mandatory minimum (truncated frame).</summary>
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TruncatedFrame,
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}
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/// <summary>Gets the reason the socket was classified desynchronized.</summary>
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public DesyncReason Reason { get; }
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/// <summary>Initializes a new instance of the <see cref="ModbusTransportDesyncException"/> class.</summary>
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/// <param name="reason">The desync reason.</param>
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/// <param name="message">A human-readable description.</param>
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/// <param name="inner">The originating exception, if any.</param>
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public ModbusTransportDesyncException(DesyncReason reason, string message, Exception? inner = null)
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: base(message, inner)
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{
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Reason = reason;
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}
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}
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