25.3. Simple Object Access Protocol (SOAP)

The Simple Object Access Protocol (SOAP) is a platform-independent protocol that uses XML to make remote procedure calls, typically over HTTP. Each request and response is packaged in a SOAP message—an XML message containing the information that a web service requires to process the message. SOAP messages are written in XML so that they’re computer readable, human readable and platform independent. Most firewalls—security barriers that restrict communication among networks—allow HTTP traffic to pass through, so that clients can browse the Internet by sending requests to and receiving responses from web servers. Thus, SOAP-based services can send and receive SOAP messages over HTTP connections with few limitations.