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| Problem | 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. | | Cause | Network issues | | Solution | 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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Product categories: Software, Application Servers, Distributed Application & Web Servers, WebSphere Application Server, HTTP Transport Operating system(s): AIX, HPUX, Linux, Multi-Platform, Solaris, Windows, Windows 2000, Windows NT, Windows Server 2003, Windows XP Software version: 3.5, 4.0, 5.0, 5.1, 6.0 Software edition: Edition Independent Reference #: 1164078 IBM Group: Software Group Modified date: 2004-03-24
(C) Copyright IBM Corporation 2000, 2004. All Rights Reserved.
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