Feature/master examples (#51)

* Initial examples/nngcat/

- C# version of https://nanomsg.github.io/nng/man/v1.1.0/nngcat.1

* Mention examples/ in README

README.md

@@ -50,7 +50,7 @@ var factory = nng.NngLoadContext.Init(ctx);
 // Use factory...
 ```
 
-See [`tests/`](https://github.com/subor/nng.NETCore/tree/master/tests) for basic examples.
+See [`tests/`](https://github.com/subor/nng.NETCore/tree/master/tests) and [`examples/`](https://github.com/subor/nng.NETCore/tree/master/examples) for usage examples.
 
 ## Build & Run
 

examples/nngcat/Program.cs

@@ -0,0 +1,85 @@
+/// <summary>
+/// C# version of nngcat.
+/// https://nanomsg.github.io/nng/man/v1.1.0/nngcat.1
+/// </summary>
+/// <example>
+/// <code>
+/// dotnet run -- --rep --listen tcp://localhost:8080 --data "42" &
+/// dotnet run -- --req --dial tcp://localhost:8080 --data "what"
+/// </code>
+/// </example>
+using Microsoft.Extensions.CommandLineUtils;
+using nng;
+using System;
+using System.IO;
+using System.Text;
+
+namespace nngcat
+{
+    class Program
+    {
+        static void Main(string[] args)
+        {
+            var app = new CommandLineApplication();
+            app.Name = "nngcat";
+            app.HelpOption("-? | -h | --help");
+            var repOpt = app.Option("--rep", "Rep protocol", CommandOptionType.NoValue);
+            var reqOpt = app.Option("--req", "Req protocol", CommandOptionType.NoValue);
+            var listenOpt = app.Option("--bind | --listen <URL>", "Connect to the peer at the address specified by URL.", CommandOptionType.SingleValue);
+            var dialOpt = app.Option("--connect | --dial <URL>", "Bind to, and accept connections from peers, at the address specified by URL.", CommandOptionType.SingleValue);
+            // Receive options
+            var quotedOpt = app.Option("-Q | --quoted", "Currently always enabled", CommandOptionType.NoValue);
+            // Transmit options
+            var dataOpt = app.Option("-D | --data <DATA>", "Use DATA for the body of outgoing messages.", CommandOptionType.SingleValue);
+
+            app.OnExecute(() => {
+                var path = Path.GetDirectoryName(typeof(Program).Assembly.Location);
+                var ctx = new nng.NngLoadContext(path);
+                var factory = nng.NngLoadContext.Init(ctx);
+
+                if (repOpt.HasValue())
+                {
+                    using (var socket = factory.ReplierOpen().listenOrDial(listenOpt, dialOpt))
+                    {
+                        var request = socket.RecvMsg().Unwrap();
+                        var str = Encoding.ASCII.GetString(request.AsSpan());
+                        Console.WriteLine(str);
+                        var reply = factory.CreateMessage();
+                        var replyBytes = Encoding.ASCII.GetBytes(dataOpt.Value());
+                        reply.Append(replyBytes);
+                        socket.SendMsg(reply);
+                    }
+                } else if (reqOpt.HasValue())
+                {
+                    using (var socket = factory.RequesterOpen().listenOrDial(listenOpt, dialOpt))
+                    {
+                        var request = factory.CreateMessage();
+                        var requestBytes = Encoding.ASCII.GetBytes(dataOpt.Value());
+                        request.Append(requestBytes);
+                        socket.SendMsg(request).Unwrap();
+                        var reply = socket.RecvMsg().Unwrap();
+                        var str = Encoding.ASCII.GetString(reply.AsSpan());
+                        Console.WriteLine('"' + str + '"');
+                    }
+                }
+                return 0;
+            });
+
+            app.Execute(args);
+        }
+    }
+
+    static class SocketExt
+    {
+        public static T listenOrDial<T>(this NngResult<T> socket, CommandOption listenOpt, CommandOption dialOpt)
+            where T: ISocket
+        {
+            if (listenOpt.HasValue())
+                return socket.ThenListen(listenOpt.Value()).Unwrap();
+            else if (dialOpt.HasValue())
+                return socket.ThenDial(dialOpt.Value()).Unwrap();
+            else
+                throw new ArgumentException("Must --listen or --dial");
+        }
+    }
+}

examples/nngcat/nngcat.csproj

@@ -0,0 +1,13 @@
+<Project Sdk="Microsoft.NET.Sdk">
+
+  <PropertyGroup>
+    <OutputType>Exe</OutputType>
+    <TargetFramework>netcoreapp3.0</TargetFramework>
+  </PropertyGroup>
+
+  <ItemGroup>
+    <PackageReference Include="Microsoft.Extensions.CommandLineUtils" Version="1.1.1" />
+    <PackageReference Include="Subor.nng.NETCore" Version="1.1.1" />
+  </ItemGroup>
+
+</Project>