Classes

Class HttpEndpoint() Professional

Class function of the HttpEndpoint class.

Description

An object of the class HttpEndpoint serves as a connection point for incoming HTTP or WebSocket connections. The connection point is active after calling the method :start(). :start() automatically creates a new thread for listening on the port associated with the HttpEndPoint. The port number must be passed as a parameter to the method :new().

For HTTP requests with a URL referring to a local file, the HttpEndpoint loads the file from the hard drive and returns it to the connected web client. The following table lists the extensions and the corresponding MIME types of the resources which are supported by default:

Default extensions and MIME types
Extension MIME type
.html text/html
.htm text/html
.gif image/gif
.png image/png
.jpg image/jpeg jpg jpe
.js application/x-javascript
.css text/css
.woff font/woff
.eot application/vnd.ms-fontobject
.otf application/octet-stream
.ttf application/octet-stream
.svg image/svg+xml
.json application/json

A web request to a resource without an extension must be handled in application code. For this, a user-defined class must be written containing the logic for handling the request. The class must have the same name as the resource which is requested, and it must be derived from a base class which corresponds to the connection type.

If the client tries to establish a websocket connection, an object of a user-defined class is created. This class must be derived from WebSocketHandler. The following URL instantiates an object from the class MyWebSocketHandler:

ws://<servername>:<port>/MyWebSocketHandler 

In case no websocket connection is to be established, an object is instantiated from a class that must be derived from the class WebHandler. The following URL instantiates an object from the class MyWebHandler, and calls the method :echo(). The parameters specified in the URL are forwarded to the handler method:

http://<servername>:<port>/MyWebHandler/echo?paramname1=value1 

The following code fragment demonstrates the implementation of the handler that corresponds to the URL above:

CLASS MyWebHandler FROM WebHandler 
  EXPORTED: 
    METHOD echo 
ENDCLASS 

<...> 

METHOD MyWebHandler:echo( cParamName1 ) 
   LOCAL cHtml 
   cHtml := "" 
   cHtml += "<html><title>MyWebHandler:echo() was called</title><body>" 
   cHtml += "Parameter cParamName1 is " + cParamName1 
   cHtml += "</body></html>" 
RETURN cHtml 

In addition to plain text connections, HTTP end points also support servicing requests via the Secure Socket Layer (SSL) protocol. For this, an SSL certificate must first be installed on the computer. Once the end point is bound to this certificate, HTTP and web socket connections to this end point can be established via SSL for increased security.

The following code fragment demonstrates the general procedure:

#define PORT 443 

// Create an end point for handling incoming 
// connections on the default port for HTTPS 
// Note: Port and address must be adjusted 
// for your environment! 
oHttpEndpoint := HttpEndpoint():new( PORT, "localhost" ) 

// Set the SSL certificate for the local computer. 
// The certificate will be used for subsequent 
// SSL connections. 
// Note: The certificate must be adjusted 
// for your environment! 
oHttpEndpoint:setCertificate( "machine\my\mycomputer" ) 

// Start the end point 
oHttpEndpoint:start() 

<...> 

Class methods
:new()
Creates an instance of the class HttpEndpoint.
:port
Contains the port number.
:address
Contains the IP number.
:lastError
Contains the error code of the last socket operation.
Connection
Configuration
:isListening()
Determines if the HttpEndpoint is currently listening.
:setCertificate()
Sets a certificate for SSL connections.
:start()
Starts the listener thread.
:stop()
Terminates the listener thread.
Examples
Implementing a web end point
// This example creates an html file in the current directory. 
// The HttpEndpoint loads the file and returns it to the 
// connected client on request. If an SSL certificate is 
// installed on the computer, the end point is bound to this 
// certificate in order to allow clients to connect via SSL 
// for increased security. 
#include "inkey.ch" 
#include "web.ch" 

#define PORT 81 
PROCEDURE Main() 
LOCAL cPort 
LOCAL oHttpEndpoint 
LOCAL nKey 
LOCAL cHtml 
LOCAL lStarted 

// 
// Creates a sample html file on the local drive. 
// 
IF .NOT. File( "default.html" ) 
   cHtml := "" 
   cHtml += "<h1>Hello World!</h1>" 
   cHtml += "<h2>Greetings from: "+AppName()+"</h2>" 
   MemoWrit( "default.html", cHtml ) 
ENDIF 

cPort := Var2Char(PORT) 
? "HttpEndpoint sample." 
? 
? "With a web browser navigate to:" 
? 
? "     http://localhost:"+cPort+"/default.html" 
? 
? "Press ESC to quit" 

// 
// Create an end point for handling incoming 
// connections on the specified port 
// 
// Note: Requests to .html files are handled 
//       automatically by the Http end point! 
//       No code must be written for returning 
//       the sample .html file. 
// 
oHttpEndpoint := HttpEndpoint():new( PORT, "localhost" ) 
lStarted := oHttpEndpoint:start() 
IF .NOT. lStarted 
  ? "Startup error. Check if port "+cPort+" is already in use." 
  WAIT 
  RETURN 
ENDIF 

// Continue after the ESC key was pressed 
nKey := 0 
DO WHILE nKey <> K_ESC 
   nKey := Inkey(1) 
ENDDO 

// 
// Stop the endpoint before the application 
// terminates 
// 
oHttpEndpoint:stop() 

RETURN 
Feedback

If you see anything in the documentation that is not correct, does not match your experience with the particular feature or requires further clarification, please use this form to report a documentation issue.