Upgrade Xp->Win7 Socket Problem

We have upgrade Pc1 from Xp->Win7
Before upgrade, the socket communication has no problem
i) Pc1 send command (3bytes) -> Pc2, Pc2 will response 3 to 20bytes
ii) Pc1 send command (3bytes) -> Pc2, Pc2 will response 1Mbytes (images data)
- this take about 25ms

After upgrade, the socket communication has problem
i) Pc1 send command (3bytes) -> Pc2, Pc2 will response 3 to 20bytes
- this has no problem
ii) Pc1 send command (3bytes) -> Pc2, Pc2 will response 1Mbytes (images data)
- pc1 receive 1024bytes
- no data for about 5sec
- pc1 receive 1024bytes
- no data for about 5sec ...
... this continue for very long

1. Pc1 did not change any hardware
2. Pc1/Pc2 did not change any s/w
3. Pc1 Nic:Intel(R) PRO/1000 PL (no change)
4. Pc2 Nic:Intel(R) 82574L Gigabit
5. Both network running at 1Gpps/Full duplex
6. Pc1 Win7 network driver:9.15.11.0

Please help...

Was the upgrade from WinXP basic or WinXP SP2?

The TCP stack in Win XP basic was changed considerably at Win XP SP2 (and beyond, including Vista and Win7). Some of the changes are described here: http://technet.microsoft.com/en-us/l.../bb457156.aspx The usual culprit (for unexpected slowdowns) was the change that allows only 10 pending half-open connection attempts (i.e., SYN sent but SYN-ACK not yet received). If this is your issue, then you will see event code 4226 in the event log ( Start, Control Panel, Administrative Tools, and Event Viewer)

If not, then show us code for PC1, 2 and 3. You symptoms also sound like you have some handshaking between PC1 and PCs2,3, and the handshaking might be the culprit.

If you cannot show actual code, then please write sample code that exhibits the problems you are seeing.

Mike