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UDP port 1025 works in XP, but not Win 7



I'm trying to capture packets from my embedded board (IP, port 1025) using UDP. It's working fine in Windows XP, but it doesn't work in Windows 7. Wireshark is still able to detect the packets coming in, but there is nothing when a UDP listener is started on the same port.

asked 10 Apr '13, 03:31

ktchiam's gravatar image

accept rate: 0%

3 Answers:


That's a Windows question really, since Wireshark is able to capture them.

answered 10 Apr '13, 03:54

Jaap's gravatar image

Jaap ♦
accept rate: 14%


Try turning the Windows Firewall off. If that fixes the issue and you want the firewall back on (as you should do generally) then you'll need to add an exception to the firewall for your app to allow the UDP traffic in.

answered 10 Apr '13, 04:19

grahamb's gravatar image

grahamb ♦
accept rate: 22%

Sorry that it's kind of Windows related, but since Wireshark can capture the packets, may be someone would know why.

I've turned off the firewall, but it still doesn't work. I've also opened up another client to send UDP packets to 1025 and it can be received. It just won't receive packets coming from my ethernet port.

(10 Apr '13, 04:23) ktchiam

Wireshark, or to be technically accurate WinPCap, captures traffic in a very different manner than a normal app would receive it.

When you say you've opened up another client to send UDP packets and they are received, was that client on the same host as the listener app, or another host?

Does your app bind it's listener to the required IP address or does it listen on all?

(10 Apr '13, 04:40) grahamb ♦


Sorry that it's kind of Windows related, but since Wireshark can capture the packets, may be someone would know why.

Probably because the packets are somehow 'damaged' and windows drops them. Take a look at the IP stats of windows. Do the counters for 'errors' increase while you are seeing the packets in Wireshark, but not in your application?

netstat -s

IPv4 Statistics

Packets Received = 1070088 Received Header Errors = 0 Received Address Errors = 271 Datagrams Forwarded = 0 Unknown Protocols Received = 0 Received Packets Discarded = 67898 Received Packets Delivered = 1108133 Output Requests = 1979878 Routing Discards = 0 Discarded Output Packets = 5809 Output Packet No Route = 1 Reassembly Required = 0 Reassembly Successful = 0 Reassembly Failures = 0 Datagrams Successfully Fragmented = 0 Datagrams Failing Fragmentation = 0 Fragments Created = 0

UDP Statistics for IPv4

Datagrams Received = 40722 No Ports = 352 Receive Errors = 67544 Datagrams Sent = 61341


answered 10 Apr ‘13, 06:06

Kurt%20Knochner's gravatar image

Kurt Knochner ♦
accept rate: 15%

edited 10 Apr ‘13, 06:08