02 October 2018

JMX Remote (visualvm)

Arguments for JVM thus VisualVM can connect remotely JMX :

-Dcom.sun.management.jmxremote
-Dcom.sun.management.jmxremote.port=9010
-Dcom.sun.management.jmxremote.local.only=false
-Dcom.sun.management.jmxremote.authenticate=false
-Dcom.sun.management.jmxremote.ssl=false


30 September 2018

TCP/IP Illustrated

RFC793 has several diagrams, in particular, from book TCP/IP Illustrated, Vol. 1: The Protocols, and concise information for this protocol.

IBM has a good replication:



Table 1. TCP state transition description table
TCP connection state Abbreviation in MVS™ console Abbreviation in TSO or UNIX shell Description
LISTEN Listen Listen Waiting for a connection request from a remote TCP application. This is the state in which you can find the listening socket of a local TCP server.
SYN-SENT SynSent SynSent Waiting for an acknowledgment from the remote endpoint after having sent a connection request. Results after step 1 of the three-way TCP handshake.
SYN-RECEIVED SynRcvd SynRcvd This endpoint has received a connection request and sent an acknowledgment. This endpoint is waiting for final acknowledgment that the other endpoint did receive this endpoint's acknowledgment of the original connection request. Results after step 2 of the three-way TCP handshake.
ESTABLISHED Estblsh Establsh Represents a fully established connection; this is the normal state for the data transfer phase of the connection.
FIN-WAIT-1 FinWt1 FinWait1 Waiting for an acknowledgment of the connection termination request or for a simultaneous connection termination request from the remote TCP. This state is normally of short duration.
FIN-WAIT-2 FinWt2 FinWait2 Waiting for a connection termination request from the remote TCP after this endpoint has sent its connection termination request. This state is normally of short duration, but if the remote socket endpoint does not close its socket shortly after it has received information that this socket endpoint closed the connection, then it might last for some time. Excessive FIN-WAIT-2 states can indicate an error in the coding of the remote application.
CLOSE-WAIT ClosWt ClosWait This endpoint has received a close request from the remote endpoint and this TCP is now waiting for a connection termination request from the local application.
CLOSING Closing Closing Waiting for a connection termination request acknowledgment from the remote TCP. This state is entered when this endpoint receives a close request from the local application, sends a termination request to the remote endpoint, and receives a termination request before it receives the acknowledgment from the remote endpoint.
LAST-ACK LastAck LastAck Waiting for an acknowledgment of the connection termination request previously sent to the remote TCP. This state is entered when this endpoint received a termination request before it sent its termination request.
TIME-WAIT TimeWt TimeWait Waiting for enough time to pass to be sure the remote TCP received the acknowledgment of its connection termination request.
CLOSED Closed Closed Represents no connection state at all.


Also, a sequence diagram, where Wikipedia is a good contribution (as usual):

- open: 3 way
- close: 4 way




http://www.icir.org/christian/sock.html

https://www.inetdaemon.com/tutorials/internet/tcp/3-way_handshake.shtml

http://www.tcpipguide.com/free/t_TCPConnectionTermination-2.htm


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