Έχω ένα project στην σχολή όπου η εργασία είναι η εξής, μια άλλη,ομάδα θα φτιάξει έναν server ,όπου σκοπός μου είναι η υλοποίησει ενός client που θα στελνει διάφορα datagrams ,όπου θα τελειώνουν με @@@ ,ανάλογα με το τί συμβαίνει σε μία βάση.
Το communication του interface έχει ως εξής :
IP is used as communications protocol
TCP datagram's are defined and sent exclusively to avoid transmission problems at network level
Client must be configured as tcp/ip client.
Α datagram has the following syntax
Size token | Token Value @@@
Packet Type Value|…….
Three @@@ character mark the end of a datagram.
The packet size indicates the length of the datagram (ASCII character string) including three @-characters in bytes. Data type :UINT
Ερώτηση 1) Τα datagrams δεν χρησιμοποιούνται μόνο με udp protocol???,
Από ένα παράδειγμα που βρήκα στο msdn για έναν asychronious client , έκανα την παρακάτω υλοποιήσει
sto module
Imports System.Net.Sockets
Imports System.net
Imports System.Text
Imports System.Net.DnsPermissionAttribute
Imports System.Security.Permissions
Public Class StateObject
' Client socket.
Public workSocket As Socket = Nothing
' Size of receive buffer.
Public Const BufferSize As Integer = 256
' Receive buffer.
Public buffer(BufferSize) As Byte
' Received data string.
Public sb As New StringBuilder
End Class 'StateObject
Public Class AsynchronousClient
' The port number for the remote device.
'Private Const port As Integer = 11000
' ManualResetEvent instances signal completion.
Public Shared connectDone As New Threading.ManualResetEvent(False)
Public Shared sendDone As New Threading.ManualResetEvent(False)
Public Shared receiveDone As New Threading.ManualResetEvent(False)
' The response from the remote device.
Private Shared response As String = String.Empty
Public Shared Sub Main(ByVal port As Integer)
' Establish the remote endpoint for the socket.
' For this example use local machine.
Dim ipHostInfo As IPHostEntry = Dns.GetHostEntry(Dns.GetHostName())
Dim ipAddress As IPAddress = ipHostInfo.AddressList(0)
Dim remoteEP As New IPEndPoint(ipAddress, port)
' Create a TCP/IP socket.
Dim client As New Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp)
' Connect to the remote endpoint.
client.BeginConnect(remoteEP, New AsyncCallback(AddressOf ConnectCallback), client)
' Wait for connect.
If client.Connected = True Then
CClient.CmdBox.Items.Add("Connected")
Else
CClient.CmdBox.Items.Add("Not Connected")
' Main("5100")
End If
' Send test data to the remote device.
Send(client, "This is a test@@@")
sendDone.WaitOne()
' Receive the response from the remote device.
Receive(client)
receiveDone.WaitOne()
' Write the response to the console.
CClient.CmdBox.Items.Add("Response received : {0}" + response)
' Release the socket.
client.Shutdown(SocketShutdown.Both)
client.Close()
End Sub 'Main
Public Shared Sub ConnectCallback(ByVal ar As IAsyncResult)
' Retrieve the socket from the state object.
Dim client As Socket = CType(ar.AsyncState, Socket)
Try
' Complete the connection.
client.EndConnect(ar)
CClient.CmdBox.Items.Add("Socket connected to {0}" + client.RemoteEndPoint.ToString())
' Signal that the connection has been made.
connectDone.Set()
Catch ex As Exception
CClient.CmdBox.Items.Add("Not Connected")
client.Close()
End Try
End Sub 'ConnectCallback
Public Shared Sub Receive(ByVal client As Socket)
' Create the state object.
Dim state As New StateObject
state.workSocket = client
' Begin receiving the data from the remote device.
client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, New AsyncCallback(AddressOf ReceiveCallback), state)
End Sub 'Receive
Public Shared Sub ReceiveCallback(ByVal ar As IAsyncResult)
Dim content As String = String.Empty
' Retrieve the state object and the client socket
' from the asynchronous state object.
Dim state As StateObject = CType(ar.AsyncState, StateObject)
Dim client As Socket = state.workSocket
' Read data from the remote device.
Dim bytesRead As Integer = client.EndReceive(ar)
If bytesRead > 0 Then
' There might be more data, so store the data received so far.
state.sb.Append(Encoding.ASCII.GetString(state.buffer, 0, bytesRead))
content = state.sb.ToString()
If content.IndexOf("@@@") > -1 Then
' Get the rest of the data.
Console.WriteLine("Read {0} bytes from socket. " + vbLf + " Data : {1}", content.Length, content)
Send(client, content)
receiveDone.Set()
Else
client.BeginReceive(state.buffer, 0, StateObject.BufferSize, 0, New AsyncCallback(AddressOf ReceiveCallback), state)
End If
End If
End Sub 'ReceiveCallback
Public Shared Sub Send(ByVal client As Socket, ByVal data As String)
' Convert the string data to byte data using ASCII encoding.
Dim byteData As Byte() = Encoding.ASCII.GetBytes(data)
' Begin sending the data to the remote device.
client.BeginSend(byteData, 0, byteData.Length, 0, New AsyncCallback(AddressOf SendCallback), client)
End Sub 'Send
Public Shared Sub SendCallback(ByVal ar As IAsyncResult)
' Retrieve the socket from the state object.
Dim client As Socket = CType(ar.AsyncState, Socket)
' Complete sending the data to the remote device.
Dim bytesSent As Integer = client.EndSend(ar)
CClient.CmdBox.Items.Add("Sent {0} bytes to server.")
' Signal that all bytes have been sent.
sendDone.Set()
End Sub 'SendCallback
End Class 'AsynchronousClient
στιν Forma
Public Class CClient
Private Sub Button1_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Connect.Click
't.workSocket = client
AsynchronousClient.Main(Port_T.Text)
End Sub
Private Sub Label2_Click(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Label2.Click
End Sub
Private Sub Form1_Load(ByVal sender As Object, ByVal e As System.EventArgs) Handles Me.Load
Srv_T.Text = "Localhost"
Port_T.Text = "5100"
End Sub
Private Sub Timer1_Tick(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles Timer1.Tick
End Sub
Private Sub Button1_Click_1(ByVal sender As System.Object, ByVal e As System.EventArgs) Handles tystr.Click
Dim ar As IAsyncResult
Dim client As Net.Sockets.Socket = CType(ar.AsyncState, Net.Sockets.Socket)
AsynchronousClient.Send(client, "TYSTRAT test @@@")
End Sub
End Class
Είναι σωστός ο τρόπος με τον οποίο στέλνω (και αν στέλνω) το datagram?
Γιατί δεν μπορώ να μέσα από έναν timer να πάρω το status του socket πχ αν είναι connected, αν έβγαλε error κπλ.?
Είναι σωστός ο τρόπος υλοποιήσεις του Client.?
Επίσης όταν τρέχω το πρόγραμμα μου κολλάει γιατί δέν βρίσκει τον server (naturally) ,πως γίνέται απλός να μου γράψει στο cmdbox ‘not connected’ και να μην κολλήσει??