How to Make an HTTP Connection Using TCP/IP with RSocket
The following code shows how to make an HTTP connection using a TCP/IP with RSocket interface which will retrieve a Web page by resolving the IP address of a server, constructing an HTTP request, sending it to the server and then receiving the response.
The sample code will show you how to:
- Open a socket and resolve the host name
- Perform the HTTP GET operation
- Display the HTTP GET status and data to the user
Note! This example does NOT send the HTTP host header so if the URL you're trying to load is on a virtual server, it won't work. Also as it says on the comments, it will disregard all file path information and converts all data into 16bit text, so it needs a lot of work to make it useful.
#include <e32std.h>
#include <es_sock.h>
#include <in_sock.h>
#include <Uri16.h>
//Two Phase Construction
CRetrieveHttp* CRetrieveHttp::NewL(MRetrieveHttpCallbacks& aCallback)
{
CRetrieveHttp* self=NewLC(aCallback);
CleanupStack::Pop(self);
return self;
}
CRetrieveHttp* CRetrieveHttp::NewLC(MRetrieveHttpCallbacks& aCallback)
{
CRetrieveHttp* self = new(ELeave) CRetrieveHttp(aCallback);
CleanupStack::PushL(self);
self->ConstructL();
return self;
}
// second-phase constructor
void CRetrieveHttp::ConstructL()
{
iState = EIdle ;
// Add self to active scheduler
CActiveScheduler::Add(this) ;
// Connect to socket server
User::LeaveIfError (iSockServer.Connect()) ;
}
// Constructor and destructor
CRetrieveHttp::CRetrieveHttp(MRetrieveHttpCallbacks& aCallback) :
CActive(0), iCallbacks (aCallback)
{
iState = EIdle ;
}
CRetrieveHttp::~CRetrieveHttp()
{
iSockServer.Close() ;
}
// Request function - Validates URL, parses out server name
// Any extra url info is ignored, port is assumed to be 80
void CRetrieveHttp::RequestL(const TDesC& aURL)
{
TUriParser url;
url.Parse(aURL);
if (url.Extract(EUriScheme).Compare(_L("http")) != 0)
{
// Invalid URL - didn't start with "HTTP://"
User::Leave(KErrArgument) ;
}
// Clear response strings
iResponse.Zero() ;
iResponseChunk.Zero() ;
iServerName.Copy(url.Extract(EUriHost));
// Construct HTTP: GET command
iRequest.Copy(_L8("GET / HTTP/1.0\r\n\r\n"));
// Open resolver socket
User::LeaveIfError (iResolver.Open(iSockServer, KAfInet, KProtocolInetTcp)) ;
// Attempt to resolve name
iResolver.GetByName(iServerName, iHostAddress, iStatus) ;
// Move to next state
iState = EResolving ;
// Enable the active object
SetActive() ;
}
// Mandatory RunL from CActive - This is the main function, basically a big switch
// statement that implements a state machine that goes through all the stages of
// performing the "GET" operation
//
void CRetrieveHttp::RunL()
{
TBool finished = EFalse ;
switch (iState)
{
case EIdle:
// Shouldn't happen
break ;
case EResolving:
// Name resolution completed - check result, if OK open socket
// and advance state to EOpening
if (iStatus == KErrNone)
{
// Recover server's IP address
TInetAddr address ;
address = iHostAddress().iAddr;
address.SetPort (80) ; // Assume always port 80 for now!
// Attempt to open the socket
if (iSocket.Open(iSockServer, KAfInet, KSockStream, KProtocolInetTcp))
{
iState =EFailed ;
finished = ETrue ;
}
else
{
iState = EConnecting ;
iSocket.Connect(address, iStatus) ;
}
}
else
{
iState = EFailed ;
finished = ETrue ;
}
break ;
case EConnecting:
// Socket sucessfully opened. Send preconstructed request to server,
// and advance state to ESending
if (iStatus == KErrNone)
{
iSocket.Write(iRequest, iStatus) ;
iState = ESending ;
}
else
{
iState = EFailed ;
finished = ETrue ;
}
break ;
case ESending:
// Request sent, Start receive process for first "chunk" of
// data and advance state to EReceiving
if (iStatus == KErrNone)
{
//iResponseLength = 0 ;
iSocket.RecvOneOrMore(iResponseChunk, 0, iStatus, iResponseChunkSizePkg) ;
iState = EReceiving ;
}
else
{
iState = EFailed ;
finished = ETrue ;
}
break ;
case EReceiving:
// If we sucessfully got a chunk then ask for more, if we've
// finished then go to complete
if (iStatus == KErrNone)
{
// Copy 8 bit characters into 16 bit response buffer
for(TInt copyPtr = 0;
(copyPtr < iResponseChunk.Length()) &&
(iResponse.Length() <
iResponse.MaxLength());
copyPtr++)
{
TChar ch = iResponseChunk[copyPtr];
// HTTP uses \r\n line termination,
//which looks funny in a CEikLabel
if (ch != '\r')
iResponse.Append (iResponseChunk[copyPtr]);
}
if (iResponse.Length() == iResponse.MaxLength())
{
// Response buffer full
iState = EComplete ;
finished = ETrue ;
}
else
{
// Issue another read request
iResponseChunk.Zero() ;
iSocket.RecvOneOrMore(iResponseChunk,
0, iStatus,
iResponseChunkSizePkg) ;
}
}
else if (iStatus == KErrEof)
{
// Server has no more data to send - We've finished!
iState = EComplete ;
finished = ETrue ;
}
else
{
iState = EFailed ;
finished = ETrue ;
}
break ;
// Either retrieve completed or oops! Close all sockets and
// free resources either way.
case EComplete:
case EFailed:
finished = ETrue ;
break ;
}
// Notify our "owner" of state change
iCallbacks.StateChange(iState) ;
if (finished)
DoCancel() ;
else
SetActive() ;
}
// Mandatory DoCancel - from CActive
void CRetrieveHttp::DoCancel()
{
// Close everything that might be open and cancel any outstanding
// operations.
iResolver.Close() ;
iSocket.CancelAll() ;
iSocket.Close() ;
}
//Method to get at the retrieved data.
TDesC &CRetrieveHttp::GetResponseData()
{
return iResponse ;
}
FYI: This was coded and tested on Sony Ericsson P800/P900.
--
This article demostrates very good example for beginenrs to study RSocket API and to make an http connection using TCP/IP with RSocket. Socket is used for end-to-end connection between two participants. Its follows client-server architecture. Sockets are useful in applications which uses bluetooth, infrared, internet or any type of connection.
The code presented in this article does an asynchronous function and the article shows the implementation for each method. The article first gives the overview and explains the task to be done and then represents the code snippest. The code is contained with comments. All the required methods are implemented.
The article can be very useful to beginenrs and intermediate developers to make an http connection using TCP/IP with RSocket.
--deepikagohil 17:40, 19 September 2009 (UTC)