Simple TIME_WAIT question

Hi all,

I've been trying to close a socket and I think it is closing now. Using
'netstat -an' I see:

tcp 0 0 127.0.0.1:1786 127.0.0.1:25
CLOSE_WAIT

Then:

tcp 0 0 127.0.0.1:25 127.0.0.1:1786
TIME_WAIT

My questions are:

1) Is it normal for a socket to transition from CLOSE_WAIT to TIME_WAIT
when the local application clears the CLOSE_WAIT condition - ie, closes
the socket?

2) What is the purpose of TIME_WAIT in Linux?

iksrazal

(E-Mail Removed) writes:

>1) Is it normal for a socket to transition from CLOSE_WAIT to TIME_WAIT
>when the local application clears the CLOSE_WAIT condition - ie, closes
>the socket?

Yes, this commonly happens.

>2) What is the purpose of TIME_WAIT in Linux?

It's tcp/ip, not just linux.

After the connection is closed, there might still be some stray
packets that were delayed and could still arrive. The TIME_WAIT
status retains a record of a recent connection, so that the system
can recognize these as delay packets.

Neil W Rickert <rickert+(E-Mail Removed)> wrote:
> (E-Mail Removed) writes:

>>1) Is it normal for a socket to transition from CLOSE_WAIT to TIME_WAIT
>>when the local application clears the CLOSE_WAIT condition - ie, closes
>>the socket?

> Yes, this commonly happens.

I thought the transition was CLOSE_WAIT -> LAST_ACK -> gone as
typically it is the first side to send a FIN who does the TIME_WAIT
(FIN_WAIT_1 -> FIN_WAIT_2 -> TIME_WAIT) and CLOSE_WAIT is the state
entered when a FIN is recieved and now awaiting the applcation to
close.

Now, that does not mean that one cannot go to TIME_WAIT from
CLOSE_WAIT, and I suppose there is the case of FIN's that cross in the
net, but I wouldn't expect the connections with crossing FIN's to pass
through CLOSE_WAIT.

rick jones
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