HttpWebRequest GetRequestStream to Amcrest camera not working - camera

Question

I have an Amcrest IP4M-1051 camera. The API for the camera enables two-way audio. Amcrest provides some freeware called, Amcrest Surveillance Pro, which demonstrates the functionality pretty well. I have a custom VB.NET WPF program in which I'm trying to replicate that functionality, using the NAudio library. My program can stream both the video and audio from the camera. I'm having trouble, though, streaming the audio picked up by my computer's microphone back to the camera. The code so far:
Imports System.Net
Imports System.Net.Sockets
Imports System.Text
Imports NAudio.Wave
Class MainWindow
Dim tcpSender As New TcpClient
Dim endPoint As Net.IPEndPoint
Dim ipAddress As Net.IPAddress
Dim port As Integer
Private Sub Window_Loaded()
'ipAddress = System.Net.IPAddress.Parse("192.168.1.80")
'port = 554
'endPoint = New Net.IPEndPoint(ipAddress, port)
'tcpSender.Connect(endPoint)
Dim waveIn As New NAudio.Wave.WaveIn
waveIn.BufferMilliseconds = 50
waveIn.WaveFormat = New WaveFormat(44100, 2)
AddHandler waveIn.DataAvailable, AddressOf NAudio_DataAvailable
waveIn.StartRecording()
End Sub
Private Sub NAudio_DataAvailable(ByVal sender As Object, ByVal e As NAudio.Wave.WaveInEventArgs)
'Dim encoded() As Byte = codec.Encode(e.Buffer, 0, e.BytesRecorded)
'audioSender.Send(encoded)
Dim buffer As Byte() = e.Buffer 'Encoding.UTF8.GetBytes(e.Buffer)
Dim bytesRecorded As Integer = e.BytesRecorded
WriteToNetwork(buffer, bytesRecorded)
End Sub
Private Sub WriteToNetwork(ByVal buffer As Byte(), ByVal bytesRecorded As Integer)
'tcpSender.Client.Send(buffer)
Dim uri As New Uri("http://admin:PASSWORD#192.168.1.80/cgi-bin/audio.cgi?action=postAudio&httptype=singlepart&channel=1")
Dim request As HttpWebRequest
request = WebRequest.CreateHttp(uri)
request.Timeout = 4000
request.Method = "POST"
request.ContentType = "Audio/G.711A"
request.ContentLength = bytesRecorded
'
'Dim postStream = request.GetRequestStream
Using postStream As IO.Stream = request.GetRequestStream
postStream.Write(buffer, 0, bytesRecorded)
'Using response As HttpWebResponse = request.GetResponse
' Dim responseString As String = New IO.StreamReader(response.GetResponseStream()).ReadToEnd
' If Not String.IsNullOrEmpty(responseString) Then
' Console.WriteLine(responseString)
' End If
'End Using
End Using
End Sub
End Class
This code has a few issues. First of all, the camera is configured to receive AAC codec, and I have to use G.711A because I couldn't get AAC to work at all. By using the G.711A, the WriteToNetwork procedure works the first time (and the camera produces a second of static) and, on the second time, hangs at request.GetRequestStream, producing error: System.Net.WebException: 'The underlying connection was closed: The connection was closed unexpectedly.' Has anyone encountered this before?