While pumping lots of records / docs / bulk inserts to the new CouchDB Server i got a mysterious connection timeout that appeared always after about 4000+ inserted records.

By using cfhttp.errorDetail i got the error:

I/O Exception: Address already in use: connect

To save you some time here is what i found.

Starting with Windows 2003 Microsoft reduced the amount of connections to user ports. I did not check it but it seems that it will be the same behaviour in Windows 2008 and Vista. Here's what Microsofts KB196271 says:

1. Start Registry Editor.
2. Locate the following subkey in the registry, and then click Parameters:
   HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters
3. On the Edit menu, click New, and then add the following registry entry:
   Value Name: MaxUserPort
   Value Type: DWORD
   Value data: 65534
   Valid Range: 5000-65534 (decimal)
   Default: 0x1388 (5000 decimal)
   Description: This parameter controls the maximum port number that is used when a program requests any available user port from the system. Typically, ephemeral (short-lived) ports are allocated between the values of 1024 and 5000 inclusive. After the release of security bulletin MS08-037, the behavior of Windows Server 2003 was changed to more closely match that of Windows Server 2008 and Windows Vista. For more information about Microsoft security bulletin MS08-037, click the following article numbers to view the articles in the Microsoft Knowledge Base:

   951746 (http://support.microsoft.com/kb/951746/ ) MS08-037: Description of the security update for DNS in Windows Server 2008, in Windows Server 2003, and in Windows 2000 Server (DNS server-side): July 8, 2008

   951748 (http://support.microsoft.com/kb/951748/ ) MS08-037: Description of the security update for DNS in Windows Server 2003, in Windows XP, and in Windows 2000 Server (client side): July 8, 2008

   953230 (http://support.microsoft.com/kb/953230/ ) MS08-037: Vulnerabilities in DNS could allow spoofing
4. Exit Registry Editor, and then restart the computer.

OK, now relax.