Retrieving HTTP header information using ActiveSocket

Introduction

ActiveSocket provides an easy-to-use development interface to a variety of IP protocols. By using ActiveSocket, you can very easily create or enhance applications with network features.

ActiveSocket features the following: ICMP, HTTP and HTTPs with support for proxy servers and secure web sites, Telnet, NTP time protocol, RSH remote shell script interface, SNMP (Simple Network Management Protcol), SNMP Traps, Sockets, WOL (Wake-On-LAN), and more.

HTTP Get and HTTP Post can be well integrated into ASP environments.
This document describes how the ActiveSocket Http object can be integrated into ASP projects.

The most important functions of the Http object are:

Connect - connect to the (remote) HTTP web server on port 80 or any alternate port; optionally, use proxy credentials to use a proxy server; optionally, specify a web account and password for password protected web sites
Disconnect - to diconnect after a connect call;
ReadData - read all data from a web page;
ReadHeader - retrieve HTTP header information.

HTTP Headers

When sending an HTTP request to a webserver, the webserver first responds with an HTTP header, followed by the HTML data.
This header can contain information about the webserver, client, cookies or proxy information.
These values can be retrieved using the 'ReadHeader' method of the Http interface.

The following lines of code demonstrate how to read some header values:

Option Explicit

Dim objHttp

Set objHttp = CreateObject ( "ActiveXperts.Http" )

objHttp.Connect "http://www.activexperts.com"

If ( objHttp.LastError <> 0 ) Then
	WScript.Echo "Failed to load website: ERROR #" & objHttp.LastError & " (" & objHttp.GetErrorDescription ( objHttp.LastError )
	WScript.Quit
End If

WScript.Echo objHttp.ReadHeader ( 37 )

objHttp.Disconnect

The samples connects to the webserver 'www.activexperts.com' and retrieves the server software version.
You can find an overview of all HTTP headers and the associated ID's to be used in the 'ReadHeader' method below.

HTTP Header ID's

Accept	24	List of MIME types supported by the client
Accept-Charset	25	List of charsets supported by the client
Accept-Encoding	26	List of encodings supported by the client
Age	48	The amount of time since the document was generated by the server
Authorization	28	Authorization credentials request
Content-Description	4	Description of the content
Content-Encoding	29	Indicates what additional content codings have been applied to the content
Content-Id	3	Content identification
Content-Length	5	Length of the content that follows
Content-Location	51	Location of the content
Content-MD5	52	MD5 Digest of the content
Content-Type	1	Content-Type of the document
Cookie	44	Cookie send by the client, if the client has received a cookie from this website before
Date	9	Date and time the content was generated on the webserver
Etag	54	Entity tag, used when the content is available on multiple locations
Host	55	Internet host and port number of the resource being requested
If-Modified-Since	32	Last time the content has been modified
Location	33	The current URL
Proxy-Authenticate	41	Authentication scheme returned by the proxy
Proxy-Authorization	61	Header that is used to identify the user to a proxy that requires authentication
Range	62	Can be used to download only a part of the content
Raw-Headers	21	All header returned by the server, separated by 0 bytes
Raw-Headers-CRLF	22	All headers returned by the server, separated by carriagereturn - linefeed bytes
Referer	35	URL of the page that linked to the current page
Request-Method	45	Request verb that was used, GET or POST
Retry-After	36	Time returned by the server, the estimated time to generate the response.
Server	37	Returns the name and version of the server software
Set-Cookie	43	Cookie received from the server
Status-Code	19	Status code returned by the server
Status-Text	20	Additional response text returned by the server
Transfer-Encoding	63	Indicates the type of transformation that has been applied on the content to transfer it to the client
User-Agent	39	Name and version of the client software
Version	18	HTTP Version of the current session (HTTP 1.0 or HTTP 1.1)
Via	66	Intermediate protocols used between the client and server, set when a proxy server is used
Warning	67	Additional information about the last request
WWW-Authenticate	40	Authetication schemes supported by the server

The ActiveSocket tool is a Network Communications ActiveX software component (SDK). This control supports SNMP, SMTP, POP3, Telnet, TCP, NTP, RSH, HTTP, HTTPs, FTP, DNS, ICMP and more, and can be used by any Windows development platform, including Visual Basic .NET, Visual CSharp .NET, ASP .NET (VB,CS), ASP, Visual Basic, Visual Studio/Visual C++, Delphi, PHP, ColdFusion, HTML, VBScript and any other ActiveX/COM compliant platform. The ActiveSocket Toolkit is an ActiveXperts Software B.V. Product.