Although Windows Store apps run in a security sandbox, the Windows Runtime provides a rich set of APIs that enable connectivity over sockets. WinRT supports the new HTML5 WebSocket specification but also allows apps to connect via TCP and UDP for real-time streaming connectivity. Join Jeremy Likness as he walks through several examples of apps using socket protocols to establish communications and demonstrates the ease of interfacing with the Windows Runtime sockets APIs.

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Windows 8.1 Sockets

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 Sockets, Simplified
 WebSockets
 UDP and TCP Sockets
 Proximity / NFC “Tap to Connect”
 Bluetooth and Wi-Fi Direct
 Recap
Agenda

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 Covers full WinRT API
 Over 80 example
projects
 This presentation is
based on Chapter 10
 Full source online at
http://winrtexamples
.codeplex.com/
 Book available at
http://bit.ly/winrtxmpl
WinRT by Example

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Sockets, Simplified
Byte

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Sockets, Simplified
Byte Array

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Sockets, Simplified
Stream
 Length (maybe)
 Position
 Read
 Write
 Seek

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Sockets Are Specialized Streams

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 Berkeley sockets released with Unix in 1983 (owned by
AT&T at the time) for “IPC” while I was writing my first
Commodore 64 programs in 6502 assembly
 Open licensing in 1989 (I had finally moved to IBM PC and
MS-DOS)
 POSIX API (Portable Operating System Interface) released
in 1988
 Windows Sockets API (WSA or Winsock) released in 1992 (I
graduated high school and discovered the Internet in
college) and later implemented for Windows
 Another F Ancillary Function Driver (AFD.sys) still exists to
this day
Sockets: A Brief History

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Sockets Are Specialized Streams

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Sockets Are Specialized Streams

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 A way to communicate between end points
 Usually operate on streams, which are
abstractions over buffers that contain bytes
 But can be a datagram that has no connection
 A socket connection has two distinct end points
 An end point is a combination of an address and
a port
 End points can be hosted on the same machine,
or different machines
Sockets Recap

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int main(void)
{
struct sockaddr_in stSockAddr;
int Res;
int SocketFD = socket(PF_INET, SOCK_STREAM, IPPROTO_TCP);
if (-1 == SocketFD)
{
perror("cannot create socket");
exit(EXIT_FAILURE);
}
memset(&stSockAddr, 0, sizeof(stSockAddr));
stSockAddr.sin_family = AF_INET;
stSockAddr.sin_port = htons(1100);
Res = inet_pton(AF_INET, "192.168.1.1", &stSockAddr.sin_addr);
(void) shutdown(SocketFD, SHUT_RDWR);
close(SocketFD);
return EXIT_SUCCESS;
}
“The Old Days” (still valid 30 yrs. later)

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 Sit on top of TCP (you’ll learn more about TCP
later)
 Operate over ports 80/443 by default (keeps
firewalls happy)
 Use HTTP for the initial “handshake”
 Provide full-duplex communications
 WinRT implementation allows for message-
based or stream-based
WebSockets

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GET /info HTTP/1.1
HOST: 1.2.3.4
Upgrade: websocket
Connection: Upgrade
Origin: http://jeremylikness.com/
HTTP/1.1 101 Switching Protocols
Upgrade: websocket
Connection: Upgrade
WebSocket Handshake
Placing my call …
Accepting ….
Now it’s streams from here on out….

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(a prime example… source code: http://bit.ly/1i5vB9p)
WebSockets

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 Both are communication protocols for delivering
octet streams (bytes!)
 UDP is fire-and-forget (connectionless)
 Individual messages sent, i.e. “datagrams”
 Fast, lots of questions: DNS, DHCP, SNMP
 TCP is connection-oriented
 TCP is stream-based
 Slower, but reliable: HTTP, FTP, SMTP, Telnet
UDP and TCP

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this.serverSocket = new StreamSocketListener();
this.serverSocket.ConnectionReceived +=
this.ServerSocketConnectionReceived;
await this.serverSocket.BindServiceNameAsync(ServiceName);
// can both read and write messages (full-duplex)
if (serverWriter == null)
{
serverWriter = new DataWriter(args.Socket.OutputStream);
serverReader = new DataReader(args.Socket.InputStream);
}
Server Listens for Connections

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var hostName = new HostName("localhost");
this.clientSocket = new StreamSocket();
await this.clientSocket.ConnectAsync(hostName, ServiceName);
clientWriter = new DataWriter(this.clientSocket.OutputStream);
clientReader = new DataReader(this.clientSocket.InputStream);
// both client and server require long-running tasks to wait for
// messages and send them as needed
while (true)
{
var data = await GetStringFromReader(clientReader);
// do something with the data
}
Client “Dials In” to Chat

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(a true adventure… source code: http://bit.ly/1j77rP3)
TCP Sockets

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 Near Field Communications (NFC) is a standard for extremely low powered
communications typically very slow and over a very small distance, between devices
and/or smart tags
 NFC is capable of sending small bursts of information. However, “tap to connect” is a
powerful mechanism for establishing a hand-shake to open a stream over other,
longer range and faster protocols like Bluetooth and Wi-Fi Direct
 Windows Runtime exposes the Proximity APIs that provide a unified way to discover
nearby devices and a protocol-agnostic mechanism to connect
 Literally you can discover, handshake, etc. and WinRT will “hand-off” a socket that is
ready to use (you won’t even know if it is over Wi-Fi Direct or Bluetooth)
 Bluetooth = short wavelength wireless technology
 Wi-Fi Direct = peer to peer over Wi-Fi (wireless cards without requiring a wireless
access point or router)
NFC and Proximity

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this.proximityDevice = ProximityDevice.GetDefault();
this.proximityDevice.DeviceArrived +=
this.ProximityDeviceDeviceArrived;
this.proximityDevice.DeviceDeparted +=
this.ProximityDeviceDeviceDeparted;
PeerFinder.ConnectionRequested +=
this.PeerFinderConnectionRequested;
PeerFinder.Role = PeerRole.Peer;
PeerFinder.Start();
var peers = await PeerFinder.FindAllPeersAsync();
var socket = await
PeerFinder.ConnectAsync(this.SelectedPeer.Information);
Proximity APIs
NFC device and events
Peer Finder (listen and browse)
Browse for peers
Connect to peer

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1. Try to get Proximity Device (NFC)
2. If exists, register to enter/leave events (NFC)
3. If it supports triggers (i.e. tap) register for connection
state change event (NFC)
4. Otherwise browse for peers (Wi-Fi Direct, Bluetooth)
5. When a peer is found, send a connection request
6. Peer must accept the connection request
7. In any scenario, once the connection exists you are
passed a stream socket and are free to communicate
Steps for Proximity

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Source code: http://bit.ly/1jlnGbB
Proximity

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 WebSockets API for simplified WebSockets
 Sockets API for TCP, UDP, Bluetooth, Wi-Fi Direct
 Windows 8.1 is capable of dialing out to any
address and port
 As a server, most practical example is listening
for Bluetooth connections
 The security sandbox prevents using sockets for
inter-app communications
Recap

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http://winrtexamples.codeplex.com/
http://bit.ly/winrtxmpl
Questions?