Question about keeping telnet connection open

[simonmason]

I have a script that connects to an Asterisk PBX and checks to see if there are any voicemails waiting. Currently I open the connection, check, and then close the connection. I was wondering how I can do the same and leave the connection open to continually check for activity. With a COM port I can use the hs.opencomport command and then specify a script file to deal with the activity that comes over the COM port. Is there a similar way to do this with an IP connection? my code is below if it helps:

Imports System.Net
Imports System.Net.Sockets
Imports System.Text

' Userid: admin
' Password: amp111

REM ACTION: LOGIN
REM USERNAME: username
REM SECRET: password
REM EVENTS: ON 

Sub Main(parms As Object)
    Telnet
end sub
 
Sub Telnet()
    dim Reply as string
    dim messages as string
    dim strpos
    dim old_messages, new_messages as string
    dim old_messages_num, new_messages_num
    dim length, strpos1, strpos2
    
    Const RemoteIP As String = "192.168.1.170"
    Const PortNumber As Integer = 5038 

    ' Connect to the Asterisk server
    Dim Client As New TcpClient()
    Client.Connect(IPAddress.Parse(RemoteIP), PortNumber)
    Dim NetStream As NetworkStream = Client.GetStream()
    Reply = ReadString(Client)
    'hs.WriteLog("debug", Reply)
    hs.WaitSecs(2)
    ' Send login command
    SendString(NetStream, "ACTION: LOGIN" & vbCrLf)
    SendString(NetStream, "USERNAME: admin" & vbCrLf)
    SendString(NetStream, "SECRET: amp111" & vbCrLf)
    SendString(NetStream, "EVENTS: ON" & vbCrLf & vbCrLf)

    Reply = ReadString(Client)
    'hs.WriteLog("debug", Reply)
    Reply = ReadString(Client)
    'hs.WriteLog("debug", Reply)

' Checking messages for 301
    SendString(NetStream, "ACTION: MailboxCount" & vbCrLf)
    SendString(NetStream, "MAILBOX: 301@default" & vbCrLf & vbCrLf)
    'Response: SuccessMessage: Mailbox Message CountMailbox: 301@defaultNewMessages: 4OldMessages: 0
    messages = ReadString(Client)
    'hs.WriteLog("debug", "301 : " & messages)
    
    'Reply = ReadString(Client)
    'hs.WriteLog("debug", Reply)
    REM Reply = ReadString(Client)
    REM hs.WriteLog("debug", Reply)


' Get old messages first:
    old_messages = right(messages, 2)
    old_messages_num = val(old_messages)
    hs.SetDeviceString("s1", old_messages_num, True)

'Get new messages second:
    strpos1 = Instr(1, messages, "s:", 1)    
    strpos2 = Instr(1, messages, "Old", 1)    
    strpos1 = strpos1 + 2
    strpos2 = strpos2 - 1
    new_messages = mid(messages, strpos1, strpos2)
    'hs.writelog("Debug", "Messages : |" & messages & "| and strpos1 : " & strpos1 & " and strpos2 : " & strpos2 & " and new_messages : " & new_messages)
    new_messages_num = val(new_messages)
    hs.SetDeviceString("s2", new_messages_num, True)

' Checking messages for 302
    SendString(NetStream, "ACTION: MailboxCount" & vbCrLf)
    SendString(NetStream, "MAILBOX: 302@default" & vbCrLf & vbCrLf)
    'Response: SuccessMessage: Mailbox Message CountMailbox: 302@defaultNewMessages: 4OldMessages: 0
    messages = ReadString(Client)
    'hs.WriteLog("debug", "302 : " & messages)
  
    'Reply = ReadString(Client)
    'hs.WriteLog("debug", Reply)
    REM Reply = ReadString(Client)
    REM hs.WriteLog("debug", Reply)


' Get old messages first:
    strpos1 = Instr(1, messages, "OldMessages:", 1)
    strpos2 = len(messages)
    strpos1 = strpos1 + 13
    'old_messages = right(messages, 2)
    old_messages = mid(messages, strpos1, strpos2)
    'hs.writelog("Debug", "old messages so far : " & old_messages)
    old_messages_num = val(old_messages)
    hs.SetDeviceString("s3", old_messages_num, True)
    'hs.writelog("Debug", "old messages : " & old_messages_num)
    
'Get new messages second:
    strpos1 = Instr(1, messages, "s:", 1)    
    strpos2 = Instr(1, messages, "Old", 1)    
    strpos1 = strpos1 + 2
    strpos2 = strpos2 - 1
    new_messages = mid(messages, strpos1, strpos2)
    ' hs.writelog("Debug", "Messages : |" & messages & "| and strpos1 : " & strpos1 & " and strpos2 : " & strpos2 & " and new_messages : " & new_messages)
    new_messages_num = val(new_messages)
    'hs.writelog("Debug", "new messages : " & new_messages_num)
    hs.SetDeviceString("s4", new_messages_num, True)

' Logout & Disconnect
    SendString(NetStream, "ACTION: logoff" & vbCrLf & vbCrLf)
    SendString(NetStream, vbCrLf)
    
' Close connection to Asterisk server
    Client.Close()

End Sub

Private Function ReadString(ByVal Client As System.Net.Sockets.TcpClient) As String
    Dim Stream As NetworkStream = Client.GetStream
    Dim Buffersize As Integer = Client.ReceiveBufferSize
    Dim Data(Buffersize -1) As Byte
    If Stream.CanTimeout Then
        Stream.ReadTimeout = 1000 * 15
    End If
    Dim BytesRead As Integer = Stream.Read(Data, 0, Buffersize)
    Return Encoding.ASCII.GetString(Data, 0, BytesRead)
End Function
 
Private Function SendString(ByVal Stream As NetworkStream, ByVal Data As String) As Boolean
    Dim Bytes As [Byte]() = Encoding.ASCII.GetBytes(Data)
    If Stream.CanTimeout Then
        Stream.WriteTimeout = 1000 * 5
    End If
    Stream.Write(Bytes, 0, Bytes.Length)
    Return True
End Function

[Michel]

Telnet Port listening

Simon,

Did you ever found a way for this. I'm facing the same issue. I can send command to a Denon amp and request status on regular basis but I'd like to have a more dynamic approach, as you described.

Thanks

Michel

[simonmason]

Sorry, I didn't. Do you connect to the Denon amp through a telnet connection or through a traditional COM connection? I gave up on the Asterisk connection - the API is extremely limited.