Update the SOAP server tutorial.

doc/SoapServerTutorial.md

@@ -4,25 +4,28 @@ Suppose you want to provide a calculator web service just like the one from [Par
 
 Firstly, create a class `CalcService` which is derived from `webcc::SoapService`, override the `Handle` method:
 ```cpp
+// calc_service.h
+
 #include "webcc/soap_service.h"
 
 class CalcService : public webcc::SoapService {
 public:
-  CalcService() = default;
-
   bool Handle(const webcc::SoapRequest& soap_request,
               webcc::SoapResponse* soap_response) override;
 };
 ```
-The `Handle` method has two parameters, one for request (input), one for response (output).
-The implementation is quite straightforward:
-- Get operation from request.
-- Get parameters from request.
+
+The `Handle` method has two parameters, one for request (input), one for response (output). The implementation is quite straightforward:
+
+- Get operation (e.g., add) from request;
+- Get parameters (e.g., x and y) from request;
 - Calculate the result.
 - Set namespaces, result name and so on to response.
 - Set result to response.
 
 ```cpp
+// calc_service.cpp
+
 #include "calc_service.h"
 
 #include "boost/lexical_cast.hpp"
@@ -40,36 +43,29 @@ bool CalcService::Handle(const webcc::SoapRequest& soap_request,
       double result = x + y;
 
       soap_response->set_soapenv_ns(webcc::kSoapEnvNamespace);
-      soap_response->set_service_ns({
-        "cal",
-        "http://www.example.com/calculator/"
-      });
+      soap_response->set_service_ns({ "cal", "http://www.example.com/calculator/" });
       soap_response->set_operation(soap_request.operation());
       soap_response->set_result_name("Result");
       soap_response->set_result(std::to_string(result));
 
       return true;
-
-    } else {
-      // NOT_IMPLEMENTED
     }
+
+    // Other operations ...
+
   } catch (boost::bad_lexical_cast&) {
-    // BAD_REQUEST
+    // ...
   }
 
   return false;
 }
 ```
 
-The `main` function would be:
+Next step, create a `SoapServer` and register `CalcService` to it with a URL.
+
 ```cpp
 int main(int argc, char* argv[]) {
-  if (argc != 2) {
-    std::cout << "Usage: " << argv[0] << " <port>" << std::endl;
-    std::cout << "  E.g.," << std::endl;
-    std::cout << "    " << argv[0] << " 8080" << std::endl;
-    return 1;
-  }
+  // Check argc and argv ...
 
   unsigned short port = std::atoi(argv[1]);
 
@@ -79,16 +75,61 @@ int main(int argc, char* argv[]) {
   try {
     webcc::SoapServer server(port, workers);
 
-    server.RegisterService(std::make_shared<CalcService>(),
-                           "/calculator");
+    server.RegisterService(std::make_shared<CalcService>(), "/calculator");
 
     server.Run();
 
   } catch (std::exception& e) {
-    std::cerr << "exception: " << e.what() << std::endl;
+    std::cerr << "Exception: " << e.what() << std::endl;
     return 1;
   }
 
   return 0;
 }
 ```
+
+The server is created with a **port number** which will be listened on to **asynchnously** accept client connections. The connections will be firstly put into a **queue** and then processed by the **worker threads**. The number of worker threads is determined by the `workers` parameter.
+
+When register service, the URL is what the clients will put in the HTTP request to access your service:
+```
+POST /calculator HTTP/1.1
+```
+
+Registering multiple services to a server is allowed, but the URL must be unique for each service.
+
+To invoke the `add` operation of the calculator service, the client HTTP request will be:
+```
+POST /calculator HTTP/1.1
+Content-Type: text/xml; charset=utf-8
+Content-Length: 263
+Host: localhost:8080
+SOAPAction: add
+
+<?xml version="1.0"?>
+<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
+        <soap:Body>
+                <ser:add xmlns:ser="http://www.example.com/calculator/">
+                        <ser:x>1.000000</ser:x>
+                        <ser:y>2.000000</ser:y>
+                </ser:add>
+        </soap:Body>
+</soap:Envelope>
+```
+
+And the HTTP response is:
+```
+HTTP/1.1 200 OK
+Content-Type: text/xml; charset=utf-8
+Content-Length: 262
+
+<?xml version="1.0"?>
+<soap:Envelope xmlns:soap="http://schemas.xmlsoap.org/soap/envelope/">
+        <soap:Body>
+                <cal:addResponse xmlns:cal="http://www.example.com/calculator/">
+                        <cal:Result>3.000000</cal:Result>
+                </cal:addResponse>
+        </soap:Body>
+</soap:Envelope>
+```
+
+See [example/soap_calc_server](example/soap_calc_server) for the full example.