UDPREADHEADER

Action

This statement reads the UDP header from the specified socket.

 

 

Syntax

UDPREADHEADER socket

 

 

Remarks

UDP packets start with a 8 byte header. This header contains the peer address, port and packet size. The UDPREADHEADER reads the header and places the information into the variables PEERADDRESS, PEERPORT and PEERSIZE.

 

After you have read the UDP header, you can use PEERSIZE to read the number of bytes available in the packet.

 

Socket is a constant or variable in the range from 0-3. And 0-7 for the W5200/W5300.

UDPREADHEADER is only available for the W5x00.

 

 

 

See also

UDPREAD, CONFIG TCPIP , TCPREADHEADER

 

 

Example

'-----------------------------------------------------------------------------------------
'name : udptest_SPI.bas
'copyright : (c) 1995-2012, MCS Electronics
'purpose : start the easytcp.exe program after the chip is programmed and
' press UDP button
'micro : Mega88
'suited for demo : no
'commercial addon needed : yes
'-----------------------------------------------------------------------------------------
 
$regfile = "m88def.dat" ' specify the used micro
 
$crystal = 8000000 ' used crystal frequency
$baud = 19200 ' use baud rate
$hwstack = 64 ' default use 32 for the hardware stack
$swstack = 64 ' default use 10 for the SW stack
$framesize = 50 ' default use 40 for the frame space
 
 
Config Spi = Hard , Interrupt = Off , Data Order = Msb , Master = Yes , Polarity = Low , Phase = 0 , Clockrate = 4 , Noss = 0
'Init the spi pins
Spiinit
 
Print "Init , set IP to 192.168.1.70" ' display a message
Enable Interrupts ' before we use config tcpip , we need to enable the interrupts
Config Tcpip = Int1 , Mac = 12.128.12.34.56.78 , Ip = 192.168.1.70 , Submask = 255.255.255.0 , Gateway = 192.168.1.1 , Localport = 5000 , Tx = $55 , Rx = $55 , Chip = W5100 , Spi = 1
 
 
 
Dim Idx As Byte ' socket number
Dim Result As Word ' result
Dim S(255) As Byte
Dim Sstr As String * 255
Dim Temp As Byte , Temp2 As Byte ' temp bytes
 
Const Showresult = 1
 
Print "UDP demo"
 
Dim Ip As Long
Ip = Maketcp(192.168.1.3) 'assign IP num
 
'like with TCP, we need to get a socket first
'note that for UDP we specify sock_dgram
Idx = Getsocket(idx , Sock_dgram , 5000 , 0) ' get socket for UDP mode, specify port 5000
Print "Socket " ; Idx ; " " ; Idx
 
'UDP is a connection less protocol which means that you can not listen, connect or can get the status
'You can just use send and receive the same way as for TCP/IP.
'But since there is no connection protocol, you need to specify the destination IP address and port
'So compare to TCP/IP you send exactly the same, but with the addition of the IP and PORT
Do
 Temp = Inkey() ' wait for terminal input
 If Temp = 27 Then ' ESC pressed
 Sstr = "Hello"
 Result = Udpwritestr(ip , 5000 , Idx , Sstr , 255)
 Elseif Temp = 32 Then 'space
 Do
 Waitms 200
 Dim Tel As Long : Incr Tel
 Sstr = "0000000000111111111122222222223333333333 " + Str(tel)
 Result = Udpwritestr(ip , 5000 , Idx , Sstr , 255)
 Loop
 End If
 Result = Socketstat(idx , Sel_recv) ' get number of bytes waiting
 If Result > 0 Then
 Print "Bytes waiting : " ; Result
 
 Udpreadheader Idx ' read the udp header
 
 #if Showresult
 Print
 Print Peersize ; " " ; Peeraddress ; " " ; Peerport ' these are assigned when you use UDPREAD
 Print Ip2str(peeraddress) ' print IP in usual format
 #endif
 
 
 If Peersize > 0 Then ' the actual number of bytes
 Print "read" ; Peersize
 Temp = Udpread(idx , S(1) , Peersize) ' read the result
 
 #if Showresult
 For Temp = 1 To Peersize
 Print S(temp) ; " " ; ' print result
 Next
 Print "done"
 #endif
 Result = Udpwrite(ip , Peerport , Idx , S(1) , Peersize) ' write the received data back
 End If
 End If
Loop
'the sample above waits for data and send the data back for that reason temp2 is subtracted with 8, the header size
 
 
End

Languages	English • Deutsch