Find which process holds a particular connection to a MySQL database

Finding which process holds a particular connection to a MySQL database is often not immediately obvious or well documented.

First do this in your mysql command line client:

mysql> show full processlist;
+-----+--------+-----------------+----------+---------+------+----------+-----------------------+
| Id  | User   | Host            | db       | Command | Time | State    | Info                  |
+-----+--------+-----------------+----------+---------+------+----------+-----------------------+
|   2 | root   | localhost       | adspider | Query   |    0 | starting | show full processlist |
| 257 | fotios | localhost:35828 | adspider | Sleep   |   20 |          | NULL                  |
| 259 | fotios | localhost:35832 | adspider | Sleep   |   17 |          | NULL                  |
| 261 | fotios | localhost:35836 | adspider | Sleep   |    3 |          | NULL                  |
| 263 | fotios | localhost:35840 | adspider | Sleep   |    1 |          | NULL                  |
+-----+--------+-----------------+----------+---------+------+----------+-----------------------+
5 rows in set (0.00 sec)

Then, on your Linux command line do this to see which process holds the socket to the port of interest:

[root@li1849-192 ~]# netstat -np | grep 35828
tcp6       0      0 127.0.0.1:35828         127.0.0.1:3306          ESTABLISHED 28509/java
tcp6       0      0 127.0.0.1:3306          127.0.0.1:35828         ESTABLISHED 28432/mysqld

In my case the connection to MySQL was being made by a java process via JDBC