Linux netstat example 2020-07-30 22:32
netstat command is used to see the network connections.
Show how many tcp connections are on the current machine.
Commonly used parameters
-a, --all Show both listening and non-listening (for TCP this means established connections) sockets. With the --interfaces option, show interfaces that are not marked --numeric , -n Show numerical addresses instead of trying to determine symbolic host, port or user names. --tpc, -t Show tcp connections -p, --program Show the PID and name of the program to which each socket belongs.
The output content is probably like this
tcp 0 0 10.145.134.204:8668 10.145.48.13:35178 TIME_WAIT - tcp 0 0 10.145.134.204:8668 10.145.117.74:36580 TIME_WAIT - tcp 0 0 10.145.134.204:8668 10.145.117.74:36862 TIME_WAIT - tcp 0 0 10.145.134.204:8668 10.145.70.134:34556 TIME_WAIT - tcp 0 0 10.145.134.204:8668 10.145.198.133:44976 TIME_WAIT - tcp 0 0 10.145.134.204:8668 10.145.159.10:40304 TIME_WAIT - tcp 0 0 10.145.134.204:8668 10.145.86.4:60560 TIME_WAIT - tcp 0 0 10.145.134.204:40244 10.145.181.202:8988 ESTABLISHED 146/java tcp 0 0 10.145.134.204:51784 10.145.170.136:8988 ESTABLISHED 146/java
Detailed explanation of the output
OUTPUT Active Internet connections (TCP, UDP, raw) Proto The protocol (tcp, udp, raw) used by the socket. Recv-Q The count of bytes not copied by the user program connected to this socket. Send-Q The count of bytes not acknowledged by the remote host. Local Address Address and port number of the local end of the socket. Unless the --numeric (-n) option is specified, the socket address is resolved to its canonical host name (FQDN), and the port number is translated into the corresponding service name. Foreign Address Address and port number of the remote end of the socket. Analogous to "Local Address." State The state of the socket. Since there are no states in raw mode and usually no states used in UDP, this column may be left blank. Normally this can be one of several values: ESTABLISHED The socket has an established connection. SYN_SENT The socket is actively attempting to establish a connection. SYN_RECV A connection request has been received from the network. FIN_WAIT1 The socket is closed, and the connection is shutting down. FIN_WAIT2 Connection is closed, and the socket is waiting for a shutdown from the remote end. TIME_WAIT The socket is waiting after close to handle packets still in the network. CLOSED The socket is not being used. CLOSE_WAIT The remote end has shut down, waiting for the socket to close. LAST_ACK The remote end has shut down, and the socket is closed. Waiting for acknowledgement. LISTEN The socket is listening for incoming connections. Such sockets are not included in the output unless you specify the --listening (-l) or --all (-a) option. CLOSING Both sockets are shut down but we still don’t have all our data sent. UNKNOWN The state of the socket is unknown.