Client-side TCP socket receiving "Address already in use" upon connect

[Steve Holden]

Tor Erik wrote:
> Tor Erik wrote:
> 
>>Fredrik Lundh wrote:
>>
>>>Tor Erik wrote:
>>>
>>>
>>>>The reason is that my application does about 16 connects and data 
>>>>transfers per second, to the same 16 remote hosts. After approx 200 
>>>>secs there are 4000 sockets waiting to be garbage collected by the OS.
>>>
>>>what does "netstat" say about these sockets ?
>>>
>>></F>
>>>
>>They are in the TIME_WAIT state... The msn library has an article on how 
>>to solve this:
>>
>>http://msdn.microsoft.com/library/default.asp?url=/library/en-us/BTS06CoreDocs/html/6987640c-1d80-4fbf-b43a-021fc8ba06a4.asp 
>>
>>
>>Summing up one could either:
>>
>>1. Increase the upper range of ephemeral ports that are dynamically 
>>allocated to client TCP/IP socket connections:
>>
>>set registry key: 
>>KEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\MaxUserPort 
>>
>>to a new DWORD value... (5000 - 65534)
>>The default in XP is 3976 -> http://support.microsoft.com/kb/Q149532
>>
>>or
>>
>>2. Reduce the client TCP/IP socket connection timeout value from the 
>>default value of 240 seconds
>>
>>set registry key:
>>HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Services\Tcpip\Parameters\TcpTimedWaitDelay 
>>
>>to a new DWORD value (30 - 300)
>>
>>The TCP RFC (RFC 793) recommends a value of 2*msl(Maximum Segment 
>>Lifetime). The general consensus about the value of msn seems to be 1-2 
>>minutes, depending on the underlying network... (2*2 min = 2*120 sec = 
>>240 sec)
>>
>>
>>I do not want to alter my registry, so I'm currently testing an idea 
>>where I let the client connect and send its content, appended with my 
>>own "magic" EOF byte-sequence. When the server receives this EOF, it 
>>takes care to close the connection. This should eliminate the problem as 
>>it is the peer closing the connection that enters the TIME_WAIT state...
>>
>>I will report my experiences...
> 
> 
> Well...  my idea does not work as expected. Even though the server 
> (remote host) calls socket.close(), it is the client that executes 
> TIME_WAIT. My guess is that the subtrates below socket closes the 
> connection at the peer calling connect regardless of where socket.close 
> is called.
> 
> Thoughts anyone?

Yes, it's the transport layer that puts the socket into the TIME_WAIT state.

regards
  Steve
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