How to open a port or reach an application on a linux server?

Question

Java

I run the JAR file on the server

java -jar myproject-1.12.jar

Successful start, port 8080

2019-11-12 15:16:17.032 INFO 1392 --- [ main] o.s.b.w.embedded.tomcat.TomcatWebServer : Tomcat started on port(s): 8080 (http) with context path ''
2019-11-12 15:16:17.099 INFO 1392 --- [ main] kz.nurzhan.Application : Started Application in 42.988 seconds (JVM running for 50.987)

command netstat -ntlp | grep LISTEN
shows the following

spoiler

tcp______0_____0_____0.0.0.0:22________0.0.0.0:*_________LISTEN_____1098/sshd
tcp______0_____0_____0.0.0.0:5432______0.0.0.0:*_________LISTEN____1188/postgres
tcp6_____0_____0_____:::8080____________:::*______________LISTEN____1392/java
tcp6_____0_____0_____:::22_______________:::*______________LISTEN____1098/sshd
tcp6_____0_____0_____:::5432____________:::*______________LISTEN____1188/postgres

port 8080 is not telnet-th not pinged
ports on the server were not closed
what could be the reason for closed access?

Answer 1

Your application only listens on IPV6, you need to tell it somewhere in the tomcat settings to listen on the "old" IPV4.