mongo --eval "JSON.stringify(db.currentOp(true))" | \
tail -n +3 | \
jq -r .inprog[].client | \
sed 's/\(.*\):.*/\1/' \
| sort | uniq -c | sort -nr

• dump connection information in standard JSON format
• remove MongoDB header
• extract IP:port as a list
• trim port
• sort IPs by freqencies