How does MySQL connect to the corresponding client process?

2020-05-19 15:31:04,976 - mysql-connector-python.mysql.connector.protocol.MySQLProtocol.make_auth - MainThread - INFO - conn-attrs {'_pid': '58471', '_platform': 'x86_64', '_source_host': 'NEEKYJIANG-MB1', '_client_name': 'mysql-connector-python', '_client_license': 'GPL-2.0', '_client_version': '8.0.20', '_os': 'macOS-10.15.3'}

4 capability flags, CLIENT_PROTOCOL_41 always set
4 max-packet size
1 character set
string[23] reserved (all [0])
string[NUL] username
 if capabilities & CLIENT_PLUGIN_AUTH_LENENC_CLIENT_DATA {
lenenc-int length of auth-response
string[n] auth-response
 } else if capabilities & CLIENT_SECURE_CONNECTION {
1 length of auth-response
string[n] auth-response
 } else {
string[NUL] auth-response
 }
 if capabilities & CLIENT_CONNECT_WITH_DB {
string[NUL] database
 }
 if capabilities & CLIENT_PLUGIN_AUTH {
string[NUL] auth plugin name
 }
 if capabilities & CLIENT_CONNECT_ATTRS {
lenenc-int length of all key-values
lenenc-str key
lenenc-str value
  if-more data in 'length of all key-values', more keys and value pairs
 }

mysql> select * from information_schema.processlist;
+----+---------+--------------------+--------------------+---------+------+-----------+----------------------------------------------+
| ID | USER | HOST | DB | COMMAND | TIME | STATE | INFO |
+----+---------+--------------------+--------------------+---------+------+-----------+----------------------------------------------+
| 8 | root | 127.0.0.1:57760 | performance_schema | Query | 0 | executing | select * from information_schema.processlist |
| 7 | appuser | 172.16.192.1:50198 | NULL | Sleep | 2682 | | NULL |
+----+---------+--------------------+--------------------+---------+------+-----------+----------------------------------------------+
2 rows in set (0.01 sec)

mysql> select * from session_connect_attrs where processlist_id = 7;               
+----------------+-----------------+------------------------+------------------+
| PROCESSLIST_ID | ATTR_NAME | ATTR_VALUE | ORDINAL_POSITION |
+----------------+-----------------+------------------------+------------------+
| 7 | _pid | 58471 | 0 |
| 7 | _platform | x86_64 | 1 |
| 7 | _source_host | NEEKYJIANG-MB1 | 2 |
| 7 | _client_name | mysql-connector-python | 3 |
| 7 | _client_license | GPL-2.0 | 4 |
| 7 | _client_version | 8.0.20 | 5 |
| 7 | _os | macOS-10.15.3 | 6 |
+----------------+-----------------+------------------------+------------------+
7 rows in set (0.00 sec)

 ps -ef | grep 58471
 501 58471 57741 0 3:24 PMttys001 0:03.67 /Library/Frameworks/Python.framework/Versions/3.8/Resources/Python.app/Contents/MacOS/Python /Library/Frameworks/Python.framework/Versions/3.8/bin/ipython