INFO: Set Winsock Control RemoteHost and RemotePort for UDP

• Microsoft Visual Basic Standard, Professional, and Enterprise Editions, 32-bit only, for Windows, version 5.0

SUMMARY

When a UDP message is received by a Winsock control, the RemoteHostIP property is set to the IP address of the remote machine, and the RemotePort property is set to the IP port of the remote UDP application. The previous properties values are overwritten.

This could create a problem if the user was not expecting data on that port from a different RemoteHostIP. Attempts to call the SendData method without setting these two properties to the appropriate values might send the data to an unplanned recipient.

Whenever a UDP socket is being used, you should always reset the RemoteHostIP and RemotePort properties to your own known values before calling the SendData method.

MORE INFORMATION

This is by design. At the Winsock layer, the sendto API requires a sockaddr structure of the remote UDP peer to send the message to, and the recvfrom API always gets a sockaddr structure for the remote UDP peer. The Winsock control internally uses the same sockaddr structure in both sendto and recvfrom API. As UDP is a connectionless protocol, it is possible that one UDP peer could receive a UDP message from a third machine unexpectedly. Therefore, it is important to reset the RemoteHostIP and RemotePort properties to your own known values before calling the SendData method.

Additional query words: kbVBp500 kbCtrl kbNetGrp kbNetwork kbWinsock kbNTOS400 kbWinOS95 kbWinOS98
kbAPI kbdss kbDSupport kbVBp

Keywords : kbGrpVB
Version : WINDOWS:5.0
Platform : WINDOWS
Issue type : kbinfo