# Synchronous Message Transfer

Use the synchronous message transfer method to transfer large messages (fire and forget), or initiate request/reply sequences to other applications or external services within the reach of ESB.

The synchronous message transfer method is typically used for request/reply scenarios. You can also use this type of message transfer for low or medium volume fire and forget scenarios.

Also, consider using the synchronous message transfer method in the following scenarios:

- When applications infrequently send large messages or are required to send messages synchronously.
- When CICS and IMS transactions publish events every few seconds.
- When sending a message to another application.

The user application would receive a dedicated listener from Substation ES to publish the messages on until it receives a signal from the sender or user application that a message is the last message to be sent or received, or until an inactivity timeout occurs.

The following figure shows the message flow of the synchronous message transfer service:

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