Using netstat to read state information on network connections
 Technote (troubleshooting)
 
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.
 
Cause
Network issues
 
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.
 
 
Cross Reference information
Segment Product Component Platform Version Edition
Application Servers Runtimes for Java Technology Java SDK
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > HTTP Transport
Operating system(s): Windows
Software version: 6.0
Software edition:
Reference #: 1164078
IBM Group: Software Group
Modified date: Sep 11, 2004