Title: Posting a web-form using TClientSocket. And how to use a web proxy-server.
Question: Posting a web form using TClientSocket. This code snipset demonstrates posting directly and thru a web proxy-server. The result returned by the server is put into a string variable (FResult).
Answer:
{
Copyright (c) 1999 by E.J.Molendijk
On the web:
http://www.delphi3000.com/article.asp?id=805
This is a code snipset showing you how to
post a form to a webserver. Look at the comments
in the source for more details.
Connect the following events to your ClientSocket:
procedure T...Form.ClientSocket1Write;
procedure T...Form.ClientSocket1Read;
procedure T...Form.ClientSocket1Disconnect;
procedure T...Form.ClientSocket1Error;
It also shows how to route the transmission
thru a web proxy-server.
This is the format used to send to the webserver:
Normal: 'POST ' + PostAddr + 'HTTP/1.0' + HTTP_Data + Content
PROXY: 'POST http://' Webserver + PostAddr + 'HTTP/1.0' + HTTP_Data + Content
}
Const
WebServer = 'www.somehost.com';
WebPort = 80;
PostAddr = '/cgi-bin/form';
{ Proxy stuff is only needed if you use a proxy: }
ProxyServer ='proxy.somewhere.com';
ProxyPort = 3128;
// Some data needed in the post heading
HTTP_Data =
'Content-Type: application/x-www-form-urlencoded'#10+
'User-Agent: Delphi/5.0 ()'#10+ { Yes! Promote Delphi 5! }
'Host: somewhere.com'#10+
'Connection: Keep-Alive'#10;
type
T...Form = class(TForm)
...
private
{ Private declarations }
HTTP_POST : String;
FContent : String;
FResult : String; // This will hold the server responce
public
{ Public declarations }
end;
{ This functions does some url-encoding on St }
{ Eg. 'John Smith' = 'John+Smith' }
function HTTPTran(St : String) : String;
var i : Integer;
begin
Result:='';
for i:=1 to length(St) do
if St[i] in ['a'..'z','A'..'Z','0','1'..'9'] then
Result:=Result+St[i]
else if St[i]=' ' then
Result:=Result+'+'
else
Result:=Result+'%'+IntToHex(Byte(St[i]),2);
end;
procedure T...Form.ClientSocket1Write(Sender: TObject;
Socket: TCustomWinSocket);
begin
// Post the data
Socket.SendText(HTTP_POST+FContent);
end;
procedure T...Form.ClientSocket1Read(Sender: TObject;
Socket: TCustomWinSocket);
begin
// Incoming result data
FResult:=FResult+Socket.ReceiveText;
end;
procedure T...Form.ClientSocket1Disconnect(Sender: TObject;
Socket: TCustomWinSocket);
begin
// YOU CAN PROCESS FResult HERE //
end;
procedure T...Form.ClientSocket1Error(Sender: TObject;
Socket: TCustomWinSocket; ErrorEvent: TErrorEvent;
var ErrorCode: Integer);
begin
ErrorCode := 0; // Ignore Errors
end;
{
And here is the routine you can call to post your form data.
}
procedure T...Form.PostTheForm;
begin
// Clear result
FResult:='';
// You can enter whatever fields you want
// These are some examples:
FContent:=
'Name='+ HTTPTran('John Smith') +'&'+
'Address='+ HTTPTran('1 Waystreet') +'&'+
'Email='+ HTTPTran('jsmith@somewhere.com') +'&'+
'B1=Submit'+
#10;
// Calculate the contents length
FContent:=
'Content-Length: '+IntToStr(Length(FContent))+#10+#10+FContent;
{-- Start proxy ---}
{ uncomment this code if you are using a proxy
ClientSocket1.Host := ProxyServer;
ClientSocket1.Port := ProxyPort;
HTTP_POST := 'POST http://'+WebServer+PostAddr+' HTTP/1.0'#10;
{--- End proxy ---}
{--- Start normal connection --- }
{ remove this code if you are using a proxy }
ClientSocket1.Host := WebServer;
ClientSocket1.Port := WebPort;
HTTP_POST := 'POST '+PostAddr+' HTTP/1.0'#10;
{--- End normal ---}
// Concat the header
HTTP_Post := HTTP_Post + HTTP_Data;
// Try to open connection
ClientSocket1.Open;
end;