使用边界定界符进行HTTP服务器响应

Question

Using Poco, I'm trying to emulate an AXIS camera web-server, that sends jpeg frames on clients request.

Each web response should be encoded with Content-Type: multipart/x-mixed-replace and a predefined boundary.

How can I do it with Poco? Thanks.

Answer 1

The response.setContentType() is rigth, but when you make the sendBuffer() , Poco doesn't put the predefined boundary strings at top of each boundary block.

It is important to specify setChunkedTransferEncoding() to false to avoid chunk transfers, that it is not what I am asking for.

What I need is this: http://www.w3.org/Protocols/rfc1341/7_2_Multipart.html

If this is my data Buffer: "This is the first boundary block. A boundary block may continue in the next block. This is the second boundary block."

This is what I need to implement:

HTTP/1.1 200 OK
Date: Tue, 01 Dec 2013 10:27:30 GMT
Content-Length: 117
Content-Type: Multipart/mixed; boundary="sample_boundary";

--sample_boundary
This is the first boundary block. A boundary block may

--sample_boundary
continue in the next block. This is the second boundary block.

Playing around with that, I see that I must to split manually my buffer in order to get the desired boundaries.

This is how I actually do it:

std::ostream& ostr = response.send();

char frameBuffer[102410];
char fragment[1024];

string boundary = "--BOUNDARY--";
response.setChunkedTransferEncoding(false);
response.setContentType("multipart/x-mixed-replace; boundary=" + boundary);


//Split my frameBuffer in some fragments with boundary
unsigned int nBytes = sizeof(frameBuffer);
unsigned int _MAX_FRAGMENT_SIZE_ = sizeof(fragment);
unsigned int index=0;

response.setContentLength(frameLength);

while (nBytes>0){

    unsigned int size = (nBytes>_MAX_FRAGMENT_SIZE_)?_MAX_FRAGMENT_SIZE_:nBytes;
    memcpy(fragment, frameBuffer + index, size);

    //Enviamos el fragmento sin mas con su boundary correspondiente.
    ostr << boundary << "\r\n";
    ostr.write(fragment, size);
    ostr << "\r\n";

    index += size;
    nBytes -= size;
}

I thought Poco had tools to solve that. Thanks

Answer 2

Something along these lines should do:

using Poco::Net::HTTPRequestHandler;
using Poco::Net::HTTPServerRequest;
using Poco::Net::HTTPServerResponse;
using Poco::Net::HTTPRequestHandlerFactory;
using Poco::Net::HTTPServerParams;
using Poco::Net::HTTPServer;
using Poco::Net::ServerSocket;
using Poco::Net::SocketAddress;

struct AXISRequestHandler: public HTTPRequestHandler
{
    void handleRequest(HTTPServerRequest& request, HTTPServerResponse& response)
    {
        // ... get data to send back
        response.setContentType("multipart/x-mixed-replace; boundary=--MY_BOUND");
        response.sendBuffer(data, size);
    }
};

struct AXISRequestHandlerFactory: public HTTPRequestHandlerFactory
{
    HTTPRequestHandler* createRequestHandler(const HTTPServerRequest& request)
    {
        return new AXISRequestHandler;
    }
};

ServerSocket svs(SocketAddress("192.168.0.1", 8080));
HTTPServerParams* pParams = new HTTPServerParams;
// ... set server params here to your liking
HTTPServer srv(new AXISRequestHandlerFactory, svs, pParams);
srv.start(); // NB: server will fly off here (to its own thread)