Telnet

We needed to issue simple commands to (and monitor) a router remotely and that's what we've been able to achieve with this little library. It's usage is simple, it doesn't do anything particularly fancy but if all you're wanting to do is interact with a telnet server by issuing commands, parsing text responses and having the opportunity to respond in code accordingly then hopefully having taken the time to wrap this up in a simple NuGet package will make your life easier!

FWIW I'm happy to take merge requests if they meet incumbent standards, don't break anything and accomodate the code file sharing so all versions work (and likely receive the same change). I'm no TCPIP/Telnet expert but if I can help out with bugs or feature requests I'll do what I can, outside my day job ofc!

v0.9 introduced a significant bump to Net versions and some potentially breaking code changes. Changes to your consuming code should be minimal, but be prepared to test thoroughly. Please raise an Issue if you encounter any problems; in part it'll help others with the same problems and we'll see what we can do to accomodate your use cases.

Usage:

    //Sync Example
    namespace PrimS.Telnet.CiTests
    {
      using FluentAssertions;
      using Xunit;
      using System;
      using System.Text.RegularExpressions;

      [TestClass]
      public class ReadMeExampleFixture
      {
        public const string Pattern =
          "(?:WAN2 total TX: )([0-9.]*) " +
          "((?:[KMG]B)|(?:Bytes))" +
          "(?:[, ]*RX: )([0-9.]*) " +
          "((?:[KMG]B)|(?:Bytes))";
        private const int TimeoutMs = 5000;

        [Fact]
        public void ReadMeExample()
        {
          using (var server = new DummyTelnetServer())
          {
            using (var client = new Client(
              server.IPAddress.ToString(),
              server.Port,
              new CancellationToken()))
            {
              client.IsConnected.Should().Be(true);
              Client.IsWriteConsole = false;
              client.TryLogin(
                "username",
                "password",
                TimeoutMs).Should().Be(true);
              client.WriteLine("show statistic wan2");
              string s = client.TerminatedRead(
                ">",
                TimeSpan.FromMilliseconds(TimeoutMs));
              s.Should().Contain(">");
              s.Should().Contain("WAN2");
              var regEx = new Regex(Pattern);
              regEx.IsMatch(s).Should().Be(true);
              MatchCollection matches = regEx.Matches(s);
              matches.Count.Should().Be(1);
              matches[0].Captures.Count.Should().Be(1);
              matches[0].Groups.Count.Should().Be(5);
              matches[0].Groups[0].Value.Should().Be(
                "WAN2 total TX: 6.3 GB ,RX: 6.9 GB");
              matches[0].Groups[1].Value.Should().Be("6.3");
              matches[0].Groups[2].Value.Should().Be("GB");
              matches[0].Groups[3].Value.Should().Be("6.9");
              matches[0].Groups[4].Value.Should().Be("GB");
            }
          }
        }
      }
    }

    // Async Example
    namespace PrimS.Telnet.CiTests
    {
      using System;
      using FluentAssertions;
      using System.Threading;
      using System.Threading.Tasks;
      using System.Text.RegularExpressions;
      using Xunit;

      public class ReadMeExampleFixture
      {
        public const string Pattern =
          "(?:WAN2 total TX: )([0-9.]*) " +
          "((?:[KMG]B)|(?:Bytes))" +
          "(?:[, ]*RX: )([0-9.]*) " +
          "((?:[KMG]B)|(?:Bytes))";
        private const int TimeoutMs = 5000;

        [Fact]
        public async Task ReadMeExample()
        {
          using (var server = new DummyTelnetServer())
          {
            using (var client = new Client(
              server.IPAddress.ToString(),
              server.Port,
              new CancellationToken()))
            {
              client.IsConnected.Should().Be(true);
              Client.IsWriteConsole = false;
              (await client.TryLoginAsync(
                "username",
                "password",
                TimeoutMs)).Should().Be(true);
              await client.WriteLineAsync("show statistic wan2");
              string s = await client.TerminatedReadAsync(
                ">",
                TimeSpan.FromMilliseconds(TimeoutMs));
              s.Should().Contain(">");
              s.Should().Contain("WAN2");
              var regEx = new Regex(Pattern);
              regEx.IsMatch(s).Should().Be(true);
              MatchCollection matches = regEx.Matches(s);
              matches.Count.Should().Be(1);
              matches[0].Captures.Count.Should().Be(1);
              matches[0].Groups.Count.Should().Be(5);
              matches[0].Groups[0].Value.Should().Be(
                "WAN2 total TX: 6.3 GB ,RX: 6.9 GB");
              matches[0].Groups[1].Value.Should().Be("6.3");
              matches[0].Groups[2].Value.Should().Be("GB");
              matches[0].Groups[3].Value.Should().Be("6.9");
              matches[0].Groups[4].Value.Should().Be("GB");
            }
          }
        }
      }
    }

    // VB.NET Example
    Private Async Function RunRemoteScript(
      commandLine As String) As Task(Of Boolean)
        Using telnet = New Client(
          "HostName",
          23,
          _cancellationSource.Token)
            If Not telnet.IsConnected Then Return False
            Dim loggedOn = Await telnet.TryLoginAsync(
              "username",
              "password",
              SocketTimeout, "#"))
            If Not loggedOn Then Return False
            Await telnet.WriteLine(commandLine)
            Dim serverResponse = Await telnet.TerminatedReadAsync(
              "#",
              TimeSpan.FromMilliseconds(SocketTimeout))
            Debug.Print(serverResponse)
            Await telnet.WriteLine("exit")
            Dim logoutMessage = Await telnet.ReadAsync(
              New TimeSpan(100))
            Debug.Print(logoutMessage)
        End Using
        Return True  ' If we got this far; celebrate
    End Function