The DSAPI libray provides a robust HTTPListener component designed to facilitate rapid development of both HTTP servers and clients. This component serves as a lightweight alternative to traditional web servers like IIS, allowing developers to handle network traffic and custom requests efficiently.

Configuring the HTTP Server

To initialize the server, instantiate the DSAPI.Network.HTTPListener class. Utilizing the WithEvents keyword allows for seamless integration of event-driven logic.

' Initialize the listener
Private WithEvents AppServer As New DSAPI.Network.HTTPListener

Sub SetupServer()
   With AppServer
       .Port = 8080
       .UsePrefix = True
       .PrefixString = "api/v1"
       .AllowExternalAccess = True
       .Start()
   End With
End Sub
   

Configuration Parameters:

• Port: Defines the network port for the listener.
• UsePrefix/PrefixString: Acts as a security mechanism. Requests must include the specified prefix in the URL path (e.g., http://localhost:8080/api/v1). If enabled, any request lacking this path structure is rejected.
• AllowExternalAccess: Determines whether the server accepts connections from outside the local machine.

Handling Server Events

The component exposes several events to manage the lifecycle and security of the connection:

Private Sub AppServer_OnRequest(client As DSAPI.Network.HTTPListener.ClientContext) Handles AppServer.OnRequest
   ' Handle legitimate client incoming data
   Dim reader As New IO.StreamReader(client.InputStream)
   Dim payload As String = reader.ReadToEnd()

   Select Case payload
       Case "status"
           AppServer.SendResponse(client, "System Online")
       Case "fetch_data"
           AppServer.SendResponse(client, IO.File.ReadAllBytes("C:\data.bin"))
       Case Else
           AppServer.SendResponse(client, "Invalid Command")
   End Select
End Sub

Private Sub AppServer_OnError(ex As Exception) Handles AppServer.OnError
   ' Log or handle server exceptions
End Sub
   

Implementing an HTTP Client

Communication can be established using standard .NET framwork networking classes. The following example demonstrates sending a POST request containing custom data to the DSAPI listener.

Public Function SendRequest(endpoint As String, port As Integer, path As String, message As String) As String
   Dim request As Net.HttpWebRequest = Net.HttpWebRequest.Create($"{endpoint}:{port}/{path}")
   Dim buffer() As Byte = System.Text.Encoding.UTF8.GetBytes(message)
   
   request.Method = "POST"
   request.ContentLength = buffer.Length
   
   Using stream = request.GetRequestStream()
       stream.Write(buffer, 0, buffer.Length)
   End Using

   Using response = request.GetResponse()
       Using reader As New IO.StreamReader(response.GetResponseStream())
           Return reader.ReadToEnd()
       End Using
   End Using
End Function
   

This implementation ensures that the payload is sent via request stream rather than exposed in the URL query string, maintaining a cleaner and more secure communication interface.