Since some parameters and values might need to be utf-8 and percent encoded (spaces, &, =, special chars…), you should rather use QUrl
(for Qt 4) or QUrlQuery
(for Qt 5) to build the posted string.
Example code for Qt 4:
QUrl postData;
postData.addQueryItem("param1", "string");
postData.addQueryItem("param2", "string");
...
QNetworkRequest request(serviceUrl);
request.setHeader(QNetworkRequest::ContentTypeHeader,
"application/x-www-form-urlencoded");
networkManager->post(request, postData.encodedQuery());
and for Qt 5:
QUrlQuery postData;
postData.addQueryItem("param1", "string");
postData.addQueryItem("param2", "string");
...
QNetworkRequest request(serviceUrl);
request.setHeader(QNetworkRequest::ContentTypeHeader,
"application/x-www-form-urlencoded");
networkManager->post(request, postData.toString(QUrl::FullyEncoded).toUtf8());
Starting with Qt 4.8 you can also use QHttpMultiPart if you need to upload files.