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Send

Sends a single HL7 message via MLLP.

Task version: 1.6.0

Required Frends version: 5.7+

Required .NET version: 8.0

Compatible Agents: Crossplatform

Source code: https://github.com/FrendsPlatform/Frends.Mllp/tree/main/Frends.Mllp.Send

Task Parameters

Name
Description

Hl7Message : String

HL7 message to send over MLLP.

Default: MSH|^&|SendingApp|SendingFac|ReceivingApp|ReceivingFac|20250101010101||ADT^A01|MSG00001|P|2.5.1\rEVN|A01|20250101010101\rPID|1||12345^^^Hospital^MR||Doe^John||19800101|M Example: MSH|^\&|SendingApp|SendingFac|ReceivingApp|ReceivingFac|20250101010101||ADT^A01|MSG00001|P|2.5.1\rEVN|A01|20250101010101\rPID|1||12345^^^Hospital^MR||Doe^John||19800101|M

Name
Description

Host : String

Hostname or IP address of the MLLP listener.

Default: 127.0.0.1 Example: 127.0.0.1

Port : Int32

TCP port of the MLLP listener.

Default: 2575 Example: 2575

TlsMode : TlsMode

The TLS encryption mode to use for the connection.

Possible values:

  • None: The TLS encryption mode to use for the connection.

  • Mtls: The TLS encryption mode to use for the connection.

Default: 0 Example: TlsMode.None

ClientCertPath : String

Path to the client certificate file (PFX or P12 format).

Required only for MTLS mode.

Default: - Example: C:\certs\client.pfx

🗝ClientCertPassword : String

Password for the client certificate.

Default: - Example: MyStrongPassword123

ConnectTimeoutSeconds : Int32

Connection timeout in seconds when opening the socket.

Default: 30 Example: 30

ReadTimeoutSeconds : Int32

Read timeout in seconds when waiting for an acknowledgement.

Default: 30 Example: 30

IgnoreServerCertificateErrors : Boolean

If enabled, the task will ignore server-side certificate validation errors.

(e.g., self-signed certificates or hostname mismatches).

Default: False Example: false

ServerCertificateThumbprints : String[]

Expected server certificate thumbprint(s) for validation.

Only used when IgnoreServerCertificateErrors is false.

Used in MTLS mode for certificate pinning.

Default: - Example: E5FA62B8B5F3B0B2B3B4B5B6B7B8B9B0B1B2B3B4

Encoding : FileEncoding

Encoding used to encode the HL7 message before sending.

Possible values:

  • UTF8: Encoding used to encode the HL7 message before sending.

  • Default: Encoding used to encode the HL7 message before sending.

  • ASCII: Encoding used to encode the HL7 message before sending.

  • Unicode: Encoding used to encode the HL7 message before sending.

  • Windows1252: Encoding used to encode the HL7 message before sending.

  • Other: Encoding used to encode the HL7 message before sending.

Default: 0 Example: FileEncoding.UTF8

EncodingInString : String

Custom encoding name, used when Encoding is set to Other.

Default: - Example: iso-8859-1

Name
Description

ValidateWithNhapi : Boolean

Validate and normalize the HL7 payload using NHapi before sending.

Default: True Example: true

ExpectAcknowledgement : Boolean

Read the acknowledgement from the listener after sending the message.

Default: True Example: true

StartBlockByte : Byte

The MLLP start-block framing byte (decimal). Default is 11 (0x0B, vertical tab).

Default: 11 Example: 11

EndBlockByte : Byte

The MLLP end-block framing byte (decimal). Default is 28 (0x1C, file separator).

Default: 28 Example: 28

CarriageReturnByte : Byte

The MLLP end-of-block trailer byte (decimal). Default is 13 (0x0D, carriage return).

Default: 13 Example: 13

MaxMessageSize : Int32

Maximum message size in bytes. Messages exceeding this limit will not be sent. 0 means unlimited.

Default: 0 Example: 1048576

AcceptableAckCodes : AcceptableAckCodes

Determines which ACK codes are considered a successful send.

Possible values:

  • All: Determines which ACK codes are considered a successful send.

  • Success: Determines which ACK codes are considered a successful send.

  • Error: Determines which ACK codes are considered a successful send.

  • Reject: Determines which ACK codes are considered a successful send.

Default: 1 Example: AcceptableAckCodes.Success

KeepConnectionAlive : Boolean

Keep the TCP connection alive and reuse it across multiple executions.

When enabled, the connection is cached for the duration of the sliding expiration window.

Default: False Example: false

ConnectionCacheExpirationMinutes : Int32

How long (in minutes) an idle cached connection is kept alive before being closed.

Only used when KeepConnectionAlive is true.

Default: 5 Example: 5

RetryCount : Int32

Number of times to retry sending the message if an error occurs. 0 means no retries (single attempt).

Default: 0 Example: 3

RetryIntervalSeconds : Int32

Delay in seconds between retry attempts. Only used when RetryCount is greater than 0.

Default: 5 Example: 5

EnableLogging : Boolean

Enable message processing logging to file.

Default: False Example: true

LogFilePath : String

File path for logging message send events. If not specified, logs to a default location.

Default: - Example: C:\Logs\mllp-messages.log

LogMessageContent : Boolean

Include full message content in logs. If false, only logs message metadata and status.

Default: False Example: false

ThrowErrorOnFailure : Boolean

Whether to throw an error on failure.

Default: True Example: false

ErrorMessageOnFailure : String

Overrides the error message on failure.

Default: - Example: Custom error message

Task Result

Name
Description

Success : Boolean

Indicates if the task completed successfully. Example: true

Output : String

Acknowledgement returned by the MLLP listener. Example: MSH|^~&|...

AckResultType : AckResultType

Classification of the received acknowledgement (Accept, Error, Reject, Invalid, or NotApplicable for one-way sends). Possible values: - Accept: Classification of the received acknowledgement (Accept, Error, Reject, Invalid, or NotApplicable for one-way sends). - Error: Classification of the received acknowledgement (Accept, Error, Reject, Invalid, or NotApplicable for one-way sends). - Reject: Classification of the received acknowledgement (Accept, Error, Reject, Invalid, or NotApplicable for one-way sends). - Invalid: Classification of the received acknowledgement (Accept, Error, Reject, Invalid, or NotApplicable for one-way sends). - NotApplicable: Classification of the received acknowledgement (Accept, Error, Reject, Invalid, or NotApplicable for one-way sends). Example: AckResultType.Accept

AckCodeValue : String

The raw acknowledgement code extracted from MSA-1 (e.g. AA, AE, AR). Null if no ACK was received or parsing failed. Example: AA

AckErrorDescription : String

Error or status description extracted from MSA-3, present on negative acknowledgements. Example: Required field PID-3 is missing

Error : Error

Error that occurred during task execution. Example: object { string Message, Exception AdditionalInfo }

Task Changelog

Changelog for Task Frends.Mllp.Send.

[1.6.0] - 2026-08-06

Changed

  • Updated copyright notice to comply with Frends standard requirements.

[1.5.0] - 2026-06-22

Added

  • Options.MaxMessageSize to reject outgoing messages exceeding a configurable size limit (0 = unlimited), logged as MESSAGE REJECTED when enabled

  • Options.KeepConnectionAlive and Options.ConnectionCacheExpirationMinutes to reuse a single MLLP connection across multiple Send executions instead of opening a new connection each time

  • Options.RetryCount and Options.RetryIntervalSeconds to automatically retry sending on failure, with a configurable delay between attempts

  • ACK parsing and classification (AckResultType: Accept, Error, Reject, Invalid, NotApplicable) based on MSA-1/MSA-3, returned via Result.AckResultType, Result.AckCodeValue, and Result.AckErrorDescription

  • Options.AcceptableAckCodes to configure which ACK classifications are treated as a successful send (All, Success, Error, Reject)

  • Options.EnableLogging, Options.LogFilePath, and Options.LogMessageContent to log message send events (sent, success, failure, rejected, retry, connection dropped, ACK failure) to file

[1.4.0] - 2026-05-06

Added

  • Options.StartBlockByte, Options.EndBlockByte, and Options.CarriageReturnByte to allow configuring MLLP framing bytes (defaults: 11, 28, 13)

[1.3.0] - 2026-04-17

Added

  • Connection.ServerCertificateThumbprints to allow pinning the expected server certificate in MTLS mode when IgnoreServerCertificateErrors is false

[1.2.0] - 2026-04-13

Changed

  • Connection.Encoding is now selectable and can be set custom by user

[1.1.0] - 2026-03-12

Added

  • Connection.Encoding parameter to allow configuring the character encoding used when sending HL7 messages (default: UTF-8)

[1.0.0] - 2026-02-05

Added

  • Initial implementation

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