how to check in linux if port is occupied?

shell> netstat -a | grep <portno>

result should be somethings similar as following

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unix  3      [ ]         STREAM     CONNECTED     3821446054 /var/run/dovecot/login/default

unix  3      [ ]         STREAM     CONNECTED     3821446052

unix  3      [ ]         STREAM     CONNECTED     3821446037

unix  3      [ ]         STREAM     CONNECTED     3821446036

unix  3      [ ]         STREAM     CONNECTED     3821442460 /var/run/dovecot/login/default

unix  3      [ ]         STREAM     CONNECTED     3821442450

unix  3      [ ]         STREAM     CONNECTED     3821442430

unix  3      [ ]         STREAM     CONNECTED     3821442429

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