TCPIP States


TCPIP States

TCP state transition description table

| TCP

| Abbreviation

| Abbreviation

| Description

| connection

| in MVS

| in TSO or

|

| state

| console

| UNIX shell

|

| LISTEN

| Listen

| Listen

| Waiting for a connection

|

|

|

| request from a remote TCP

|

|

|

| application. This is the

|

|

|

| state in which you will find

|

|

|

| a local TCP server's

|

|

|

| listening socket.

| 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

|

|

|

| should normally be 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 should

|

|

|

| normally be 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.