#Build2016

Using the right networking APIs for your Universal Windows appSidharth Nabar, Himadri SarkarWindows Networking team

Server-side support

Scenario requirement

s

Foreground vs

background

Portability requirement

s

Performance consideratio

nsEase of coding

Considerations when writing a networking app

Which API should you use?

Discuss 4 networking scenarios & API Choices for each

In this talk

HTTPS with user authentication

Device-Cloud bi-directional communication

Network communication between devices over socketsDownload/Upload content to cloud in the background

HTTPS with User Authentication

Scenario 1

• Client Authentication• Username/Password or certificate?• UI or Programmatic?

• Server Authentication• Well-known or private CA?• Custom validation/Certificate pinning?

Features

Recommended API: HttpClient

Windows.Web.Http & System.Net.HttpAPI Choices

Feature Windows.Web.Http

System.Net.Http

Programming Language support All UWP languages C#/VB

Private CA/Self-signed certificate √ √Custom validation of server certificate

√ (new!) X (on roadmap)

Integration with native UI for Auth

√ X

Client Certificate Support √ Partial

Cross-platform support (Xamarin)

X √

Programming Pattern – Windows.Web.Http1. Create an HttpBaseProtocolFilter instance (optional)

var filter = new HttpBaseProtocolFilter();

2. Modify settings on the filter (optional)

filter.ClientCertificate = myCertificate;

3. Create an HttpClient instance

var client = new HttpClient(); ORvar client = new HttpClient(filter);

4. Send requests from client

HttpResponseMessage response = await client.GetAsync(uri);

Demo: Online Auction AppRequirements:1. Custom server certificate validation2. Client Certificate

API Choice:Windows.Web.Http.HttpClient

Summary: HTTPS with User Authentication• Windows.Web.Http

Supports wide range of HTTP security and authentication features

Available for all UWP programming languages

• System.Net.Http Supports programmatic use of credentials and certificatesAvailable cross-platform for C#/VB developers

(For more info and code snippets, see http://aka.ms/httpclientblogpost)

Device-Cloud Bidirectional

Communication

Scenario 2

• Communication Model• Truly bidirectional or client-initiated?• Half-duplex or full-duplex?

• Server Endpoint• REST API or simple message exchange?• Supports WebSockets?

• Performance Requirements/Optimizations• Caching/Data Compression required?• Latency/delay requirements?

Features

Windows.Web.Http.HttpClient&Windows.Networking.Sockets.WebSockets

API Choices

Feature HttpClient WebSockets

Messaging pattern Request-response Bidirectional

Duplex communication? Half Full

Latency/overhead Higher Lower

Proxy/Firewall traversal √ √Server certificate custom validation

√(new!) √ (new!)

REST support, CRUD semantics Built-in Needs additional code

Caching and data compression Built-in Needs additional code

MessageWebSocket & StreamWebSocket

API Choices (Contd.)

Feature MessageWebSocket

StreamWebSocket

Message Format Discrete WebSocket messages

Continuous data stream

UTF-8 Strings/JSON data √ X

Binary data √ √

Recommended data size Small (bytes/KB) Large (MB)

Recommended content types Strings, JSON content

Audio, Video, Photos

Programming Pattern – MessageWebSocket1. Create an instance of WebSocket

var socket= new MessageWebSocket();

2. Register MessageReceived event handler

socket.MessageReceived = myReceivingHandler;

3. Register Closed event handler

socket.Closed = myClosedHandler;

4. Connect to server and send data. Close connection with status code at the end.

await socket.ConnectAsync(serverUri);// Send data.socket.Close(code, reason);

Demo: Online Auction AppRequirements:1. Client-Server bidirectional communication2. Server relays others’ bids independent of

client’s bids3. Minimum latency and overhead

API Choice:Windows.Networking.Sockets.MessageWebSocket

Network Traffic Comparison

Wireshark trace for WebSocket run

Wireshark trace for HttpClient runBytes on the wire

Summary: Device-Cloud bidirectional communication• HttpClient

Ideal for request-response communicationBuilt-in support for REST API and message handling semantics

• WebSockets Ideal for low latency bidirectional communicationMessage format and semantics need to be implemented on top

Network communication between devices over

sockets

Scenario 3

• Lifespan of the socket• Foreground only or Background also

• Language Choice• C#/VB, JavaScript or C++

• Pre-existing code• Win32 or .NET libraries

Features

API Choices

Feature Windows.Networking.Sockets

System.Net.Sockets

WinSock

Language Support

C++/CX √ X √JavaScript

√ X X

C#/VB √ √ XActivity Support in Background

√ X X

Windows.Networking.Sockets, System.Net.Sockets and Winsock

•Special trigger to start a background task – SocketActivityTrigger

•App can transfer ownership of socket to the OS while suspending

•OS keeps the socket alive even when the app is not running

Sockets – Listening in Background

Programming Pattern – Sockets in Background1. Create a task with trigger type SocketActivityTrigger

socketTaskBuilder.TaskEntryPoint = "SocketActivityBackgroundTask.SocketActivityTask";var trigger = new SocketActivityTrigger();socketTaskBuilder.SetTrigger(trigger);var task = socketTaskBuilder.Register();

2. Associate Socket with the task and connect to the remote device

socket.EnableTransferOwnership(task.TaskId, SocketActivityConnectedStandbyAction.Wake); await socket.ConnectAsync(target, port);

Things to note:• At any point ownership of the socket can be only in one

component• Find the list of sockets owned by the service using:

SocketActivityInformation.AllSockets• Socket not in the list means socket is already closed or

retrieved

Programming Pattern – Sockets in Background3. Transfer the ownership

when suspending foreground app or Background Task cancellation

socket.TransferOwnership(socketId);

Demo: Multi-player GameRequirements:1. App communication between devices over sockets2. Listening on the socket activity even when the app is

not running

API Choice:Windows.Networking.Sockets

• Sockets APIs in UWPRecommended: Windows.Networking.SocketsAlso available: System.Net.Socket, Winsock

• Listening on Socket in backgroundUse SocketActivityTrigger

Summary

Download/Upload content to cloud in the background

Scenario 4

• Protocol• HTTP/ FTP

• Destination location• Memory/File

• Content Size• Small (in KBs)/Big (in MBs)

• Resiliency to reboot and network outage• Resource Awareness• Battery/Network cost

Features

HttpClient (in background task) & BackgroundTransfer

API Choices

Feature HttpClient in BG Task Windows.Networking.Backgroun

dTransferProtocol HTTP HTTP/FTPDestination Location In memory & File File onlyRecommended file size Small (KBs) Large (MBs)

Resiliency (network connection drop/reboot)

Needs additional code Can be resumed where left off

Network Cost Awareness Needs additional code Built-inBattery Saver Awareness Needs additional code Built-in

Programming Pattern – Windows.Networking.BackgroundTransfer1. Create an DownloadOperation instance

BackgroundDownloader downloader = new BackgroundDownloader(); DownloadOperation download = downloader.CreateDownload(new Uri(downloadlocation), file);

2. Start the transfer Task<DownloadOperation> startTask = download.StartAsync().AsTask();

3. Retrieve and attach to the transfers

downloads = await BackgroundDownloader.GetCurrentDownloadsAsync();await download.AttachAsync().AsTask(cts.Token, progressCallback);

Programming Pattern – Windows.Networking.BackgroundTransfer4.Handling of Completion in foreground app

Task<DownloadOperation> startTask = download.StartAsync().AsTask();Task continueTask = startTask.ContinueWith(OnDownloadCompleted);

5.Handling of Completion using a background task

BackgroundTransferCompletionGroup completionGroup = new BackgroundTransferCompletionGroup();//Create background task builderbuilder.SetTrigger(completionGroup.Trigger);BackgroundDownloader downloader = new BackgroundDownloader(completionGroup);

Demo: Multi-player GameRequirements:1. Download a new game level in the Background2. Show a toast notification on completion of the

download

API Choice:Windows.Networking.BackgroundTransfer

• BackgroundTransfer APIs in UWPRecommended for large files For smaller size/in-memory content - HTTPClient in background task

• Automatic completion handlingUse trigger in BackgroundTransferCompletionGroup

Summary – Download/Upload content in Background

• MSDN: http://aka.ms/NetworkApiChoice• GitHub Universal Samples:

https://github.com/Microsoft/Windows-universal-samples/• HttpClient• WebSockets• SocketActivityStreamSocket• BackgroundTransfer

• API Feedback: http://aka.ms/WinDevUserVoice

References and More Info

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Thank You!