MICROSOFT_PRESS_EBOOK_PROGRAMMING_WINDOWS_8_APPS_WITH_HTML_CSS_AND_JAVASCRIPT_PDF

}
// The protocol here is simple: a four-byte 'network byte order' (big-endian) integer that
// says how long a string is, and then a string that is that long. We wait for exactly 4 bytes,
// read in the count value, and then wait for count bytes, and then display them.
function startServerRead() {
socketsSample.serverReader.loadAsync(4).done(function (sizeBytesRead) {
// Make sure 4 bytes were read.
if (sizeBytesRead !== 4) { /* [Show message] */ }
// Read in the 4 bytes count and then read in that many bytes.
var count = socketsSample.serverReader.readInt32();
return socketsSample.serverReader.loadAsync(count).then(function (stringBytesRead) {
// Make sure the whole string was read.
if (stringBytesRead !== count) { /* [Show message] */ }
// Read in the string.
var string = socketsSample.serverReader.readString(count);
socketsSample.displayOutput("Server read: " + string);
}
// Restart the read for more bytes. We could just call startServerRead() but in
// the case subsequent read operations complete synchronously we start building
// up the stack and potentially crash. We use WinJS.Promise.timeout() to invoke
// this function after the stack for current call unwinds.
WinJS.Promise.timeout().done(function () { return startServerRead(); });
}); // End of "read in rest of string" function.
}, onError);
This code is structured to wait for incoming data that isn’t ready yet, but you might have situations in
which you want to know if there’s more data available that you haven’t read. This value can be obtained
through the DataReader.unconsumedBufferLength property.
In Scenario 2, the data-sending side of the relationship is simple: create a StreamSocket and call
connectAsync (js/connectToListener.js; note that onError uses StreamSocketError.getStatus again):
socketsSample.clientSocket = new Windows.Networking.Sockets.StreamSocket();
socketsSample.clientSocket.connectAsync(hostName, serviceName).done(function () {
// ...
}, onError);
Sending data in Scenario 3 takes advantage of a DataWriter built on the socket’s output stream
(js/sendData.js):
var writer = new Windows.Storage.Streams.DataWriter(socketsSample.clientSocket.outputStream);
var string = "Hello World";
var len = writer.measureString(string); // Gets the UTF-8 string length.
writer.writeInt32(len);
writer.writeString(string);
writer.storeAsync().done(function () {
writer.detachStream();
}, onError);
682