This is the exception I encountered whenever I run load test against HTTP or Web Service Requests using JMeter.

I am running 120 concurrent threads using a Windows based notebook.

After searching, I found that this problem is Windows based. There is a article at http://support.microsoft.com/kb/q196271, which says Windows XP only will make outbound TCP/IP connections using ports 1024-5000, and takes up to 4 minutes to recycle them. Therefore, if you do a lot of connections in a short amount of time, you
can easily eat that port range up.

The steps

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. 

4. Exit Registry Editor, and then restart the computer.

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