Status of TCP connections

Status of TCP connections

The status of a TCP connection can be one of the following:

established
The TCP connection has been accepted by the remote party and is still active.
closed
The TCP connection has been closed after being successfully established.
no service
The remote party acknowledged the initial SYN message by a RST message; i.e. the remote party does exist, but no service is bound to the request port. Note: Most personal computers are protected by a firewall that discards RST messages to prevent effective port scanning.
no host
The remote party does not acknowledge the SYN message; i.e. the remote party does not exist or it is protected by a firewall.
rejected
The TCP connection was rejected by the operating system itself; for instance due to security settings.
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