3.2.2 Sequence of Events
The following diagram shows the sequence of events for a 'Hello World' application using Windows Communication Foundation (WCF).

Figure 17: Sequence diagram for Hello World!!
The client sends a SayHello request.
The code example shows the HTTP headers of the request message.
POST /Hello HTTP/1.1.. Content-Type: text/xml; charset=utf-8.. SOAPAction: "http://tempuri.org/IHelloWorldService/SayHello".. Host: 10.185.189.63..Content-Length: 163.. Expect: 100-continue.. Accept-Encoding: gzip, deflate.. Connection: Keep-Alive....
The code example shows the body of the message.
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"> <s:Body> <SayHello xmlns="http://tempuri.org/"> <name>world!!</name> </SayHello> </s:Body> </s:Envelope>
The SOAP Body element contains the method name to be called and the input arguments.
The server responds with the "Hello World!!" string.
The code example shows the HTTP headers of the response message.
HTTP/1.1 200 OK. .Content-Length: 206. .Content-Type: text/xml; charset=utf-8.. Server: Microsoft-HTTPAPI/2.0.. Date: Tue, 21 Sep 2010 22:02:33 GMT....
The code example shows the SOAP response message.
<s:Envelope xmlns:s="http://schemas.xmlsoap.org/soap/envelope/"> <s:Body> <SayHelloResponse xmlns="http://tempuri.org/"> <SayHelloResult>Hello, world!!</SayHelloResult> </SayHelloResponse> </s:Body> </s:Envelope>
The SOAP response contains an entry for SayHelloResponse that contains the response string: "Hello World!!"