Sort command in unix with numeric sort

sort expects whitespace separated fields. To get it to sort on the port, you should change the field separator:

sort -t: -nk2 file

Here, I am telling sort to take : as the field separator. Therefore the first characters of the second field are the port number and it sorts as you want it to:

$ sort -t: -nk2 file
tcp        0      0 192.168.0.210:22        0.0.0.0:*  LISTEN  2223/sshd
tcp        0      0 192.168.0.210:25        0.0.0.0:*  LISTEN  3589/master
tcp        0      0 192.168.0.210:80        0.0.0.0:*  LISTEN  2037/apache
tcp        0      0 192.168.0.210:110       0.0.0.0:*  LISTEN  3385/dovecot
tcp        0      0 192.168.0.210:143       0.0.0.0:*  LISTEN  3385/dovecot
tcp        0      0 192.168.0.210:443       0.0.0.0:*  LISTEN  2037/apache
tcp        0      0 192.168.0.210:587       0.0.0.0:*  LISTEN  3589/master

The output of awk contains only one column, so no 16th column.

So sort sees all identical empty sort keys and what you observe is the result of the last resort sort (lexical sort on the whole line) which you can disable with the -s option in some implementations.

Here you want:

awk -F'[:,]' '{print $16}' test.json | sort -n

Now, if you want to sort the file on the 16^th column, beware sort supports only one character column delimiter, so you'd need to preprocess the input:

sed 's/[:,]/&+/g' test.json | sort -t+ -k16,16n | sed 's/\([:,]\)+/\1/g'

Here appending a + to every : or ,, sorting with + as the column delimiter and removing the + afterwards.