My Tech Blog

In windows XP and windows Vista, Microsoft still enforce and limit the maximum simultaneous half-open outbound TCP connection attempts per second that the system can make in order to protect the system being used by malicious software, such as viruses and worms, to spread to uninfected computers, or to launch distributed denial of service attack (DDoS).

The number of TCP connection attempts are limited differently by different version of windows. For example, windows XP SP2 has 10 maximum incomplete concurrent connections attempts limit per second, Windows Vista Home Basic has maximum limit of 2 and Vista Ultimate has 25 per second.

This is why heavy P2P (peer-to-peer) applications such as uTorrent, BitComet, Thunder, eMule, etc, or P2PTV such as PPLive, PPStream, Sopcast, etc may face some error or slow download and upload speed due to these limitations.

However there are some some tools to fix or to crack the TCP concurrent connection limit in Windows XP, Vista & 7.