Qt: Use tcp socket to get google map image? -


for reason need use blocking call perform image accessing google's server. however, qnetworkaccessmanager seems async, though there many work arounds, calling eventloop.exec(); many people online suggested me not so.

so trying use tcp socekt. want access image here:

http://mt1.google.com/vt/lyrs=y&x=0&y=0&z=0

and here code:

socket = new qtcpsocket(this);      socket->connecttohost("mt1.google.com", 80, qiodevice::readwrite);      if(socket->waitforconnected(5000))     {         qdebug() << "connected!";          // send         socket->write("/vt/lyrs=y&x=0&y=0&z=0");         socket->waitforbyteswritten(1000);         socket->waitforreadyread(3000);          qdebug() << "reading: " << socket->bytesavailable();          // data         qdebug() << socket->readall();          // close connection         socket->close();     }     else     {         qdebug() << "not connected!";     }

but seems working @ all? should write through tcp socket image?

tcp provides transport mechanism. since trying communicate web server, should compose http messages.

replace line 

socket->write("/vt/lyrs=y&x=0&y=0&z=0");

with

socket->write("get /vt/lyrs=y&x=0&y=0&z=0 http/1.1\r\nhost: mt1.google.com\r\nuser-agent: testagent\r\n\r\n");

and should following response :

http/1.1 200 ok date: sun, 14 jun 2015 14:24:40 gmt expires: sun, 14 jun 2015 14:24:40 gmt cache-control: private, max-age=3600 access-control-allow-origin: * content-type: image/jpeg x-content-type-options: nosniff server: paintfe content-length: 10790 x-xss-protection: 1; mode=block x-frame-options: sameorigin alternate-protocol: 80:quic,p=0  imagedata

parse response , extract imagedata part.

edit : tcp delivers response divided chunks. approach, not able receive whole response since trying receive in 1 go.

you should examine content-length header , wait until receiveing specified amount of bytes.


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