WSDL - Solicit-Response

1. What is Solicit-Response?

In a solicit-response operation, the service provider initiates the communication instead of the client.

  • The service provider sends a request to the service consumer.

  • The service consumer processes the request and sends a response back to the provider.

Analogy:
It’s like your bank calls you to verify a transaction, and you reply with confirmation.

2. Solicit-Response in WSDL

In a WSDL portType definition, a solicit-response operation has:

  • An <output> message first → sent by the service provider.

  • An <input> message → sent back by the service consumer.

Example WSDL (Solicit-Response Operation)

<portType name="NotificationPortType">
  <operation name="TransactionVerification">
    <output message="tns:TransactionRequest"/>
    <input message="tns:TransactionResponse"/>
  </operation>
</portType>

  • Output message: Sent first by the service provider.

  • Input message: Sent later by the service consumer.

3. Solicit-Response SOAP Example

Step 1 — Service Provider Sends Request

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
                  xmlns:txn="http://bank.example.com/transaction">
   <soapenv:Header/>
   <soapenv:Body>
      <txn:TransactionRequest>
         <txn:transactionID>56789</txn:transactionID>
         <txn:amount>5000</txn:amount>
      </txn:TransactionRequest>
   </soapenv:Body>
</soapenv:Envelope>

Step 2 — Service Consumer Sends Response

<soapenv:Envelope xmlns:soapenv="http://schemas.xmlsoap.org/soap/envelope/"
                  xmlns:txn="http://bank.example.com/transaction">
   <soapenv:Header/>
   <soapenv:Body>
      <txn:TransactionResponse>
         <txn:status>Approved</txn:status>
      </txn:TransactionResponse>
   </soapenv:Body>
</soapenv:Envelope>

4. Solicit-Response Workflow

  1. Service Provider initiates communication → Sends a request.

  2. Service Consumer receives request → Processes it.

  3. Consumer sends back response → Confirms or denies the request.

  4. Provider processes response.

5. Use Cases for Solicit-Response

This pattern is less common than request-response but useful when the server must start the interaction.

Examples

  • Bank fraud alerts → Bank requests confirmation of a transaction.

  • Shipment notifications → Logistics provider asks receiver for delivery confirmation.

  • Real-time event processing → Stock exchange pushes price updates to brokers.

6. Solicit-Response vs Request-Response

Feature Solicit-Response Request-Response
Who initiates Service provider Service consumer
First message Sent by provider Sent by consumer
Second message Sent by consumer Sent by provider
WSDL Input Comes second Comes first
WSDL Output Comes first Comes second
Use cases Alerts, notifications Data fetching, API calls

7. Real-Life Analogy

  • Solicit-Response:
    A bank calls you asking, “Do you confirm this transaction?” → You reply yes or no.

  • Request-Response:
    You call the bank asking for your account balance → The bank responds.

8. Summary

  • Solicit-Response = Service provider initiates communication.

  • The provider sends a request, the consumer sends a response.

  • WSDL defines it with <output> first and <input> second.

  • Useful for alerts, notifications, and real-time systems.

  • Less common compared to request-response.