What is this port? and It's changed

[hsunryou]

now I check the service port of Asterisk. and I have a something i don’t understand.
i hope that someone help me!
(sorry for my not good english)

Asterisk Service Port is ‘49150’ like below

[root@JBPDS01 mantech]# netstat -anp --inet6
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp6       0      0 :::22                   :::*                    LISTEN      1189/sshd           
...  
udp6       0      0 :::16010                :::*                                1880/jsvc.exec      
udp6       0      0 :::49150                :::*                                13364/asterisk

after restarting asterisk, Service Port is changed( 49150 → 57575 )
I didn’t set any config file.
what is this port ?

[root@JBPDS01 mantech]# systemctl restart asterisk
[root@JBPDS01 mantech]# 

[root@JBPDS01 mantech]# netstat -anp --inet6      
Active Internet connections (servers and established)
Proto Recv-Q Send-Q Local Address           Foreign Address         State       PID/Program name    
tcp6       0      0 :::22                   :::*                    LISTEN      1189/sshd           
...
udp6       0      0 ::1:323                 :::*                                1085/chronyd        
udp6       0      0 :::57575                :::*                                13554/asterisk  

[ldo]

Dynamic ports are usually a sign of a client-side connection. E.g. for DNS requests.