Below netstat commands are helpful while troubleshooting the Socket timeout issue.
- · netstat -ie -- to show all interfaces
- · netstat –r -- show current rounting table
- · netstat –C -- show the current active connection
- · netstat -at -- show all the current connection,
-l -- listen on local machine
-p -- processes
- · netstat -tanp | grep PID
- · netstat -nap | grep :Port
Most
of the 11 TCP states are easy to understand and most programmers know what they
mean:
CLOSED: There is
no connection.
LISTEN: The local
end-point is waiting for a connection request from a remote end-point i.e. a
passive open was performed.
SYN-SENT: The
first step of the three-way connection handshake was performed. A connection
request has been sent to a remote end-point i.e. an active open was performed.
SYN-RECEIVED: The
second step of the three-way connection handshake was performed. An
acknowledgement for the received connection request as well as a connection
request has been sent to the remote end-point.
ESTABLISHED: The
third step of the three-way connection handshake was performed. The connection
is open.
FIN-WAIT-1: The
first step of an active close (four-way handshake) was performed. The local
end-point has sent a connection termination request to the remote end-point.
CLOSE-WAIT: CLOSE_WAIT
means the operating system knows that the remote application has closed the
connection and waits for the local application to also do so.
FIN-WAIT-2: The
remote end-point has sent an acknowledgement for the previously sent connection
termination request. The local end-point waits for an active connection
termination request from the remote end-point.If the count is high then may be
there is some issue, application is not closing the connection properly. Lots
of FIN-WAIT-2 connection ead to a memory overflow.
LAST-ACK: The
local end-point has performed a passive close and has initiated an active close
by sending a connection termination request to the remote end-point.
CLOSING: The
local end-point is waiting for an acknowledgement for a connection termination
request before going to the TIME-WAIT state.
TIME-WAIT: The
local end-point waits for twice the maximum segment lifetime (MSL) to pass
before going to CLOSED to be sure that the remote end-point received the
acknowledgement
