C#
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rdavisau

Description

Cross-platform socket API for Xamarin iOS/Android/Forms, Xamarin.Mac/MonoMac, Windows Phone 8/8.1, Windows Store and Windows Desktop.

217 Stars 77 Forks MIT License 179 Commits 58 Opened issues

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Sockets Plugin for Xamarin and Windows (PCL)

Join the chat at https://gitter.im/rdavisau/sockets-for-pcl

An abstraction over the socket helper classes of .NET and WinRT, providing a PCL-friendly socket library for projects targeting Xamarin iOS/Android/Forms, Xamarin.Mac, Windows Phone 8/8.1, Windows Store, UWP, and Windows Desktop. It allows you to write socket code in your PCL, simplifying cross-platform peer-to-peer communications significantly as well as enabling code sharing for many other use cases.

This library utilises the "Bait and Switch" pattern, so must be installed via NuGet in both the PCL and your native projects.

Get it on NuGet:

Install-Package rda.SocketsForPCL

Classes

The plugin currently provides the following socket abstractions:

Class

Description .NET Abstraction WinRT Abstraction
TcpSocketListener Bind to a port and accept TCP socket connections. TcpListener StreamSocketListener
TcpSocketClient Connect to a TCP endpoint with bi-directional communication. TcpClient StreamSocket
UdpSocketReceiver Bind to a port and receive UDP messages. UdpClient DatagramSocket
UdpSocketClient Send messages to arbitrary endpoints over UDP. UdpClient DatagramSocket
UdpSocketMulticastClient Send and receive UDP messages within a multicast group. UdpClient DatagramSocket

Apart from the decisions made in order to merge the two APIs, the abstraction aims to be relatively unopinionated. This means that there is little to no protection in the library against socket failures, reliablity, retry, and other considerations. sockethelpers-for-pcl is a longer term project with the aim of providing useful functionality around the base sockets-for-pcl classes, including hub-style communications, custom protocol helpers and support for typed messaging, and error handling/life cycle and reliability options.

Example Usage

TcpSocketListener
and
TcpSocketClient
each expose
ReadStream
and
WriteStream
properties of type
System.IO.Stream
for receiving and sending data.
UdpReceiver
,
UdpClient
and
UdpMulticastClient
expose a
MessageReceived
event and a
Send()
method due to the nature of the transport and the underlying implementations.
A TCP listener
var listenPort = 11000;
var listener = new TcpSocketListener();

// when we get connections, read byte-by-byte from the socket's read stream listener.ConnectionReceived += async (sender, args) => { var client = args.SocketClient;

var bytesRead = -1;
var buf = new byte[1];

while (bytesRead != 0)
{
    bytesRead = await args.SocketClient.ReadStream.ReadAsync(buf, 0, 1);
    if (bytesRead > 0)
        Debug.Write(buf[0]);
}

};

// bind to the listen port across all interfaces await listener.StartListeningAsync(listenPort);

A TCP client
var address = "127.0.0.1";
var port = 11000;
var r = new Random(); 

var client = new TcpSocketClient(); await client.ConnectAsync(address, port);

// we're connected! for (int i = 0; i<5; i++) { // write to the 'WriteStream' property of the socket client to send data var nextByte = (byte) r.Next(0,254); client.WriteStream.WriteByte(nextByte); await client.WriteStream.FlushAsync();

// wait a little before sending the next bit of data
await Task.Delay(TimeSpan.FromMilliseconds(500)); 

}

await client.DisconnectAsync();

A UDP receiver
var listenPort = 11011;
var receiver = new UdpSocketReceiver();

receiver.MessageReceived += (sender, args) => { // get the remote endpoint details and convert the received data into a string var from = String.Format("{0}:{1}", args.RemoteAddress, args.RemotePort); var data = Encoding.UTF8.GetString(args.ByteData, 0, args.ByteData.Length);

Debug.WriteLine("{0} - {1}", from, data);

};

// listen for udp traffic on listenPort await receiver.StartListeningAsync(listenPort);

A UDP client
var port = 11011;
var address = "127.0.0.1";

var client = new UdpSocketClient();

// convert our greeting message into a byte array var msg = "HELLO WORLD"; var msgBytes = Encoding.UTF8.GetBytes(msg);

// send to address:port, // no guarantee that anyone is there // or that the message is delivered. await client.SendToAsync(msgBytes, address, port);

A multicast UDP client
var port = 11811;
var address = "239.192.0.1"; // must be a valid multicast address

// typical instantiation var receiver = new UdpSocketMulticastClient(); receiver.TTL = 5;

receiver.MessageReceived += (sender, args) => { var from = String.Format("{0}:{1}", args.RemoteAddress, args.RemotePort); var data = Encoding.UTF8.GetString(args.ByteData, 0, args.ByteData.Length);

Debug.WriteLine("{0} - {1}", from, data);

};

// join the multicast address:port await receiver.JoinMulticastGroupAsync(address, port);

var msg = "HELLO MULTIVERSE"; var msgBytes = Encoding.UTF8.GetBytes(msg);

// send a message that will be received by all listening in // the same multicast group. await receiver.SendMulticastAsync(msgBytes);

Binding to a specific interface

For a majority of mobile use cases, binding to all interfaces is a good approach. However, when working with multicast or on a machine with many interfaces, it may be useful to bind to a specific interface. The

TcpSocketListener
,
UdpSocketReceiver
and
UdpSocketMulitcastClient
classes include an optional
CommsInterface
parameter on their listen/join methods, allowing them to be bound to a specific interface only. If this parameter is not specified, all interfaces will be bound.
CommsInterface
has a static method
GetAllInterfacesAsync
that can be used to enumerate the available interfaces. ```csharp // retrieve the list of interfaces from the device var allInterfaces = await CommsInterface.GetAllInterfacesAsync();

// get the first interface with an ip address var firstUsable = allInterfaces.FirstOrDefault(ci => ci.IsUsable);

if (firstUsable == null) return; // no connected interfaces, too bad!

var listener = new TcpSocketListener(); await listener.StartListeningAsync(11000, firstUsable);

Console.WriteLine("Listening on interface with ip: {0}", firstUsable.IpAddress); ```

TLS Support

TcpSocketClient
supports TLS connections (server certificate only). Pass
true
to the optional parameter
useTls
on
ConnectAsync
to enable secure communication.

Platform Considerations

  • On Windows Phone, you will require appropriate permissions in your app manifest. Depending on whether you are listening or sending, this could include a combination of
    privateNetworkClientServer
    ,
    internetClient
    and/or
    internetClientServer
    capabilities.
  • On Windows Phone/Store, there are restrictions regarding passing traffic over loopback between separate apps (i.e. no IPC)
  • Binding to specific interfaces is not supported on Windows Phone 8.0 (8.1 is fine). All interfaces will be bound, even if a specific
    CommsInterface
    is provided.

Additional 'higher level' features will likely end up in the sockethelpers-for-pcl project mentioned earlier.

Contributions

Many members of the community have contributed to improving sockets-for-pcl:

  • @rdavisau
  • @jamesmontemagno (project and NuGet templates)
  • @galvesribeiro (TLS support)
  • @SatoshiARA (Mac support)
  • @aghajani (bugfixes)
  • @danielcweber (
    GetStream()
    , PCL-friendly
    SocketException
    )
  • @xen2 (configurable and consistent buffering between .NET and WinRT)
  • @NVentimiglia (bugfixes, design considerations)
  • @fubar-coder (auto/ephemeral port selection, support for getting connected interface)
  • @mattleibow (Xamarin Component Store submission)
  • @Waty (proper events, bugfixes)
  • @SparkStream (TcpSocketClient cancellation support, service name support)
  • @usasos000 (bugfixes)
  • @jasells (udpclient design considerations)
  • @vbisbest (prelease testing, bugfixes)
  • @1iveowl (udp multicast considerations)

If you have a bugfix or a feature you'd like to add, please open an issue. All pull requests should be opened against the

dev
branch.

Sponsors

Thanks to Xamarin and ReSharper who provide open-source licenses for the project.

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