Graphics 800, 600
SetBuffer BackBuffer()
Inp_Port = 4000
Out_Port = 4001
ip_count = CountHostIPs(GetEnv("localhost"))

Repeat
   Text 0, 0, "Sample UDP Communications"
   Text 0, 10, "LOCAL IP:"
   For i = 1 To ip_count
      Text 0, 20, DottedIP(HostIP(1))
   Next
   Text 0, 30, "Enter Destination IP#: xxx.xxx.xxx.xxx"
   Dest_IP$ = NewInput$(Dest_IP$)
   Text 0, 40, ">" + Dest_IP$ + "|"
   Flip 
   Cls
Until KeyDown(28)

IP = INT_IP(Dest_IP$)
udp_rd = CreateUDPStream(Inp_Port)
udp_wr = CreateUDPStream(Out_Port)
Repeat
   
   Text 0, 40, "Starting Chat... Press ESC to quit"
   
   byte1 = GetKey()
   If byte1>0 Then
      If Byte1 = 13 Then
         WriteByte(udp_wr, byte1) ;Bytes werden an den Port 4000 gesendet?
         SendUDPMsg udp_wr, IP, Inp_Port
      Else
         drawedSendText$ = drawedSendText$ + Chr(Byte1)
         WriteByte(udp_wr, byte1)
         SendUDPMsg udp_wr, IP, Inp_Port
      EndIf
   EndIf

   IP_rd = RecvUDPMsg(udp_rd)

   If IP_rd <> 0 Then
      Buflen = ReadAvail(udp_rd)
      If Buflen> 0 Then
         byte1 = ReadByte(udp_rd) ;Bytes werden aus dem Port 4001 gelesen?!
         If byte1 <> 13 Then
            drawedRecText$ = drawedRecText$ + Chr$(byte1)
         EndIf
      EndIf
   EndIf
   Text 0, 50, drawedSendText$
   Text 0, 60, drawedRecText$
   Flip
   Cls
Until KeyDown(1) 


CloseUDPStream udp_wr
CloseUDPStream udp_rd
End

Function INT_IP(IP$)
   a1 = Int(Left(IP$, Instr(IP$, ".") - 1)) : IP$ = Right(IP$, Len(IP$) - Instr(IP$, "."))
   a2 = Int(Left(IP$, Instr(IP$, ".") - 1)) : IP$ = Right(IP$, Len(IP$) - Instr(IP$, "."))
   a3 = Int(Left(IP$, Instr(IP$, ".") - 1)) : IP$ = Right(IP$, Len(IP$) - Instr(IP$, "."))
   a4 = Int(IP$)
   Return (a1 Shl 24) + (a2 Shl 16) + (a3 Shl 8 ) + a4
End Function

Function NewInput$(currentText$)
   localChar = GetKey()
   If (localChar > 0) And (localChar <> 8 ) Then
      currentText$ = currentText$ + Chr$(localChar)
   ElseIf localChar = 8 Then
      length = Len(currentText)
      If length > 0 Then
         currentText = Left(currentText, length - 1)
      EndIf
   EndIf
   Return currentText$
End Function