Looking for half-open concurrent TCP connections limit patcher? Microsoft introduces a limit (of 10) to restrict number of allowed simultaneous outgoing half-open TCP connections in Windows XP SP2 in a bid to prevent virus or malicious program to make unlimited infectious connections to other system when a PC is compromised. The limit continues to exist in Windows Vista RTM and SP1. Result is event ID 4226 with error message “TCP/IP has reached the security limit imposed on the number of concurrent TCP connect attempts”, and fanatic search for patched TCPIP.sys or half-open TCP connections limit memory value crack by many Windows users, especially P2P and torrent downloaders.
Microsoft appears to have a change of heart on the half-open outbound TCP connection attempts limit with the release of Windows Vista SP2 and Windows 7, probably due to the fact that the limit never effective in stopping the spreading of worms and viruses, or Microsoft has grown more confident about security feature of newer operating system.
According to Notable Changes in Windows Server 2008 SP2 and Windows Vista SP2 document published in conjunction with the release of SP2 RTM:
SP2 removes the limit of 10 half open outbound TCP connections. By default, SP2 has no limit on the number of half open outbound TCP connections.
The complete removal of the limit for half-open outbound TCP connections, which is defaulted to 10, was finalized with the release of Windows Server 2008 and Vista SP2 Build 17506. In fact, the half-open outgoing TCP connection limit has been bypassed by default since Windows Vista SP2 RC Build 16670. Previously, the changelog of SP2 showed that Microsoft looks like going to “add a registry key that enables modification of the maximum number of open TCP connections to increase application compatibility”.
Instead, Microsoft adds a registry key that allows user or administrator to enable (turn on) or disable (turn off) the half-open TCP connections limit in Windows Vista with Service Pack 2 and in Windows Server 2008 with Service Pack 2.