Using netstat to read state information on network connections
 Technote (FAQ)
 
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.
 
 
 


Document Information


Product categories: Software > Application Servers > Distributed Application & Web Servers > WebSphere Application Server > HTTP Transport
Operating system(s): HP-UX
Software version: 4.0
Software edition:
Reference #: 1164078
IBM Group: Software Group
Modified date: Mar 24, 2004