I'm aware that Tomcat uses ports 8080, 8009, and 8005. But recently I used netstat to see the ports Tomcat was using, and noticed that the PID of the Tomcat service was listening on multiple ports, it looked like this (the 2281 PID belongs to the Tomcat service)
Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name
tcp6 0 0 :::41020 :::* LISTEN 2281/java
tcp6 0 0 :::34300 :::* LISTEN 2281/java
tcp6 0 0 :::34621 :::* LISTEN 2281/java
tcp6 0 0 :::37150 :::* LISTEN 2281/java
tcp6 0 0 :::43231 :::* LISTEN 2281/java
tcp6 0 0 :::34847 :::* LISTEN 2281/java
tcp6 0 0 :::40512 :::* LISTEN 2281/java
tcp6 0 0 :::35808 :::* LISTEN 2281/java
tcp6 0 0 :::35168 :::* LISTEN 2281/java
tcp6 0 0 :::33984 :::* LISTEN 2281/java
tcp6 0 0 :::44577 :::* LISTEN 2281/java
tcp6 0 0 :::34145 :::* LISTEN 2281/java
tcp6 0 0 :::46786 :::* LISTEN 2281/java
tcp6 0 0 :::44419 :::* LISTEN 2281/java
tcp6 0 0 :::40291 :::* LISTEN 2281/java
tcp6 0 0 :::41091 :::* LISTEN 2281/java
tcp6 0 0 127.0.0.1:8005 :::* LISTEN 2281/java
tcp6 0 0 :::36903 :::* LISTEN 2281/java
tcp6 0 0 :::39624 :::* LISTEN 2281/java
tcp6 0 0 :::36072 :::* LISTEN 2281/java
tcp6 0 0 :::38825 :::* LISTEN 2281/java
tcp6 0 0 :::8009 :::* LISTEN 2281/java
CodePudding user response：
It is a fairly standard practice for a long lived process that listens on a single port (for example, 80) to spawn a child thread on a second port when a new, long lived connection is established.
For example,
- client sends message to server:80
- server spawns a child thread on a new port and directs the client to that new port.
- future messages between the client and server are via the new port.
My guess is that you have some number of keep alive connections to your Tomcat server.
CodePudding user response：
lsof utility a thread dump could help to find which thread is opening the port
lsof -Pawn -iTCP -sTCP:LISTEN -K -F pfKMT0 -p 11630 c 15 | tr '\000' ' ' | grep -v '^f'
Output sample
p11630
p11630 K11636 Mjava
p11630 K11646 MVM Thread
p11630 K11647 MReference Handl
p11630 K11648 MFinalizer
p11630 K11692 Mhttp-nio-8080-e
p11630 K11693 Mhttp-nio-8080-e
p11630 K11694 Mhttp-nio-8080-e
p11630 K11695 Mhttp-nio-8080-e
p11630 K11696 Mhttp-nio-8080-e
Fields can be read as
p11630 PID of tomcat (prefixed by 'p')
K11696 THREAD PID (prefix=K)
Mhttp-nio-8080-e Thread name (prefix=M)
Alternative with awk
lsof -Pawn -iTCP -sTCP:LISTEN -K -p 11630 c 15 | gawk '{print $1,$2,$3,$4,$11 }'
COMMAND PID TID TASKCMD NAME
java 11630 11636 java *:8080
java 11630 11636 java 127.0.0.1:8009
java 11630 11636 java 127.0.0.1:8005
java 11630 11636 java *:37961
CodePudding user response：
Check Tomcat's configuration file server.xml for connectors (HTTP/1.1, HTTP/2, AJP).
Another thing is that applications (war files) deployed on Tomcat can also open ports if they so choose.
And the JVM could open yet another port when debugging or JMX gets activated. So you also want to check the concise command line used to run Tomcat.
Netstat will show the sum of those.