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The following section describes what the Receive Agent is and what its responsibility is:

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Agent Responsibility

The Receive Agent is a "connection-point" to other MSH instances. This agent will receive AS4Message's that are being sent form other MSH's. During the receive operation, the incoming AS4Message will be verified if it has a valid signature, if the possible attachments are correctly encrypted, ... All these verification options (and others) are configured in a Receiving Processing Mode.

Message Flow

When an AS4Message is received by the agent it goes through a series of steps:

1. Determine the Receiving Processing Mode that must be used to correctly process the incoming message.Each configured Receiving Processing Mode is inspected and assigned a score. 
   The Receiving Processing Mode that best matches the received AS4Message will be used to further process the AS4Message.
   

   IMPORTANT: If none of the configured Receiving Processing Modes sufficiently match the received AS4Message, or if it is impossible to select just one matching Receiving Processing Mode, then the Agent will stop processing the received AS4Message right here since it is not possible to correctly process the message.

2. When a Receiving Processing Mode is selected, the received message will be validated. The validation consists of the following rules:

   • The SOAP body of the AS4Message should be empty
   • Each ParttInfo element should have an unique href reference to a embedded payload (href that starts with 'cid:')
   • Each included Attachment should reference a PartInfo



3. After the validation, the included Attachment's (if any) will be decrypted using the information found in the assigned Receiving Processing Mode (decryption algorithm that must be used, the certificate that must be used to decrypt, ...). Decryption only takes place if this is allowed by the pmode: this means that the Decryption option must be set to Required or Allowed. When the Decryption option is set to Ignored, the received message will not be decrypted. When Decryption is set to NotAllowed the Receive Agent will respond with an Errorsignalmessage if the message is encrypted.

4. After the message is possibly decrypted, the Agent verifies if the signature (if present) is valid. This is only done when the Signature option in the pmode is set to Required or Allowed. In the case of Ignored or NotAllowed the verification will not take place or isn't allowed at all.

   Note: for incoming Non-Repudiation Receipt's, the Receiving Processing Mode has an option (VerifyNRR) to also verify the included references.

   
   

5. After the signature has been verified, the included Attachments's (if any) will be decompressed.

   Note: if the incoming message must be forwarded, the attachments will not be decompressed.

   
   

6. Finally, when the message has been successfully processed, the receive agent will create a Receipt signalmessage. This Receipt will be created conforming the settings that can be found in the Receiving Processing mode. (ReceiptHandling.UseNRRFormat to specify if NRI information must be included and the Signing.IsEnabled setting in the responding pmode (which is defined by the ReplyHandling.SendingPMode element)). This Receipt will then be sent to the sender.

Next to that, the Receive Agent will make sure that the received AS4Message is delivered or forwarded, depending on what is configured in the MessageHandling section in the Receiving Processing Mode.

If any of the above described steps fail for any reason: not matched Receiving Processing Mode, decryption failure, signature invalid, ... an Error will be created that includes the failure message. This Error will be signed if the Receiving Processing Mode is configured this way (Signing.IsEnabled is set to true).

Agent Trigger

The Receive operation is triggered each time the configured Receiver receives an AS4Message. This Receiver will act as the "entry-point" of the agent. If no AS4Message is received, the Receive operation will be triggered but the agent will respond with an error saying an unexpected message is received.

Static Receive Agent

The Receive Agent can be configured as a Static Receive Agent. This requires you to pre-configure the Receive Agent with a specifiec Receiving Processing Mode. A Static Receive Agent will only allow UserMessages to be received, SignalMessages will be rejected. For each received AS4Message, the specified Receiving Processing Mode will be used during the Receive Operation and no determination of a Receiving Processing Mode will take place.

To configure a Static Receive Agent, do the following:

• Go to the configuration of the Receive Agent you want to make static.
• Make sure the Transformer is a ReceiveMessageTransformer
• The setting ReceivingPMode will be appear
• Specify the Receiving Processing Mode by selecting one of the configured pmodes

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