WxHTTP

Functions Missing from Docs

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Functions found in src/common/http.cpp that you need to know about but that aren't documented in wxHTTP.

bool Abort(void)

Aborts an active transfer by closing the connection.

bool Connect(const wxString& host, unsigned short port)

These do not make an actual connection to a server but simple tell wxHTTP about the server you want to request pages from.

void SetPostBuffer(const wxString& post_buf)

Set the data to be posted to the server.

wxString GetContentType()

Get the "Content-Type" header returned by the server.

void SetProxyMode(bool on)

Set whether or not to use a proxy.

void ClearHeaders()

Removes all headers.

wxInputStream *GetInputStream(const wxString& path)

Get a page from the server specified by the last call to Connect(...). Path is path to a resource on the server not a full URL.

Note: You must call one of the Connect functions at least once before using this function or the result will be NULL.

Basic Usage

#include <wx/sstream.h>
#include <wx/protocol/http.h>

wxHTTP get;
get.SetHeader(_T("Content-type"), _T("text/html; charset=utf-8"));
get.SetTimeout(10); // 10 seconds of timeout instead of 10 minutes ...

// this will wait until the user connects to the internet. It is important in case of dialup (or ADSL) connections
while (!get.Connect(_T("www.google.com")))  // only the server, no pages here yet ...
    wxSleep(5);

wxApp::IsMainLoopRunning(); // should return true

// use _T("/") for index.html, index.php, default.asp, etc.
wxInputStream *httpStream = get.GetInputStream(_T("/intl/en/about.html"));

// wxLogVerbose( wxString(_T(" GetInputStream: ")) << get.GetResponse() << _T("-") << ((resStream)? _T("OK ") : _T("FAILURE ")) << get.GetError() );

if (get.GetError() == wxPROTO_NOERR)
{
    wxString res;
    wxStringOutputStream out_stream(&res);
    httpStream->Read(out_stream);

    wxMessageBox(res);
    // wxLogVerbose( wxString(_T(" returned document length: ")) << res.Length() );
}
else
{
    wxMessageBox(_T("Unable to connect!"));
}

wxDELETE(httpStream);
get.Close();

Known issues

100% CPU Usage

Sometimes, when you try to use wxHTTP to get a file and the main loop is not running, your CPU usage comes to 100% and this overhead completely freeze your Windows (This issue doesn't appear under wxGTK). A small clue is in the wxApp documentation : wxAppConsole::IsMainLoopRunning : "This can be useful to test whether the events can be dispatched. For example, if this function returns false, non-blocking sockets cannot be used because the events from them would never be processed." It looks like you can't use wxHTTP even in blocking mode until you are in main loop (at least on Windows platform).

So you should always test for being inside main loop before using wxHTTP (certainly other protocols too).

I was able to use wxHTTP successfully from a wxThread on Windows XP (wxWidgets 2.8.4). The important step was to create the wxHTTP object outside the thread and call Initailise() from outside the thread too. I may have been fortunate as in this application the main thread was not very busy.

One possible workaround for this issue:

BEGIN_EVENT_TABLE(ClassName, wxFrame)
        //[...]
	EVT_IDLE(ClassName::OnIdle)
END_EVENT_TABLE()
//[...]

void ClassName::Init()
{
        //[...]
        // initialized in header file as bool firstIdle;
	firstIdle = true;
}
//[...]

void ClassName::OnIdle(wxIdleEvent &event)
{
	if (firstIdle)
	{
		[...];
                // if content was changed, show the window after that
		Show(true);

		firstIdle = false;
	}

	event.Skip();
}