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Problem(Abstract) |
Analyzing the state of network connections can contribute
to resolving problems with application connectivity. Using netstat -an
provides a list of connections and their state. |
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Cause |
Network issues |
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Resolving the
problem |
The following is sample output using one of the
netstat option:
# netstat -an
Active Internet connections (including servers)
Proto Recv-Q Send-Q Local Address Foreign Address
(state)
tcp4 0 0 *.13
*.*
LISTEN
tcp 0 0 *.21
*.*
LISTEN
tcp 0 0 *.23
*.*
LISTEN
tcp4 0 0 *.25
*.*
LISTEN
tcp4 0 0 127.0.0.1.49213
*.* LISTEN
tcp4 0 0 *.6000
*.*
LISTEN
tcp4 0 0 *.6112
*.*
LISTEN
tcp4 0 0 9.27.40.28.32774
9.27.40.28.716 ESTABLISHED
tcp4 0 0 9.27.40.28.716
9.27.40.28.32774 ESTABLISHED
...
The states are defined as follows:
- CLOSED
Connection is closed.
- LISTEN
Listening for a connection.
- SYN_SENT
Active; sent SYN. Waiting for a matching connection request after having
sent a connection request.
- SYN_RCVD
Sent and received SYN. Waiting for a confirming connection request
acknowledgment after having both received and sent connection requests.
- ESTABLISHED
Connection established.
- CLOSE_WAIT
Received FIN; waiting to receive CLOSE.
- LAST_ACK
Received FIN and CLOSE; waiting for FIN ACK.
- FIN_WAIT_1
Closed; sent FIN.
- CLOSING
Closed; exchanged FIN; waiting for FIN.
- FIN_WAIT_2
Closed; FIN is acknowledged; awaiting FIN.
- TIME_WAIT
In 2 MSL (twice the maximum segment length) quiet wait after close.
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Cross Reference information |
Segment |
Product |
Component |
Platform |
Version |
Edition |
Application Servers |
Runtimes for Java Technology |
Java SDK |
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