Re: Tomcat9 not listening to ipv4 port 8080, only ipv6

Tue, 28 Nov 2023 10:40:12 -0800 

Christoph,

On 11/28/23 09:53, Christoph Kukulies wrote:

That was my connector:

  <Connector port="8080" protocol="HTTP/1.1"
                connectionTimeout="20000"
                redirectPort="8443" />
I triednetstat -tulpn as well and it could be seen there was  no listener under ip4 and port 8080.
If you use the "address" attribute, you can pick the interface you will listen to: 

"
[address]
For servers with more than one IP address, this attribute specifies which address will be used for listening on the specified port. By default, the connector will listen all local addresses. Unless the JVM is configured otherwise using system properties, the Java based connectors (NIO, NIO2) will listen on both IPv4 and IPv6 addresses when configured with either 0.0.0.0 or ::. The APR/native connector will only listen on IPv4 addresses if configured with 0.0.0.0 and will listen on IPv6 addresses (and optionally IPv4 addresses depending on the setting of ipv6v6only) if configured with ::. 
" [1]
You have not specified an "address", so you get the default which should be "all local addresses". You only showed your lsof output, so I couldn't see which interface you had been bound to. 

-chris
[1] https://tomcat.apache.org/tomcat-9.0-doc/config/http.html#Standard_Implementation
Am 28.11.2023 um 15:15 schrieb Christopher Schultz <ch...@christopherschultz.net <mailto:ch...@christopherschultz.net>>: 

Christoph,

On 11/28/23 08:26, Christoph Kukulies wrote:

not that I kew of (changes in JVM arguments). I will try your suggestion:
-Djava.net.preferIPv4Stack=true
and thanks, it helped:
I put it into /etc/defaults/tomcat9 (under Ubuntu 22.04)
JAVA_OPTS="-Djava.awt.headless=true -Djava.net.preferIPv4Stack=true"
and now I have:
root@mail:/etc/default# lsof -i :8080
COMMAND   PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
java    59579 tomcat   37u  IPv4 579485      0t0  TCP *:http-alt (LISTEN)
root@mail:/etc/default#


So... is that what you wanted?

What does your <Connector> configuration look like?
Try using netstat instead of lsof. It will show you the network interface being used as well as the port number and IP stack type. 

-chris
Am 28.11.2023 um 13:58 schrieb Suvendu Sekhar Mondal <suv3...@gmail.com <mailto:suv3...@gmail.com> <mailto:suv3...@gmail.com>>: 

Hello Christoph,
On Tue, Nov 28, 2023, 5:55 PM Christoph Kukulies <k...@kukulies.org.invalid <mailto:k...@kukulies.org.invalid>> 
wrote:
I'm pulling my hairs on a suddenly occured - possibly - misconfiguration. 
But I can't find it out:

catalina.2023-11-28.log:


28-Nov-2023 13:15:43.742 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Server version name: 
 Apache Tomcat/9.0.58 (Ubuntu)
28-Nov-2023 13:15:43.743 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Server built:
 Jan 6 1970 15:09:28 UTC
28-Nov-2023 13:15:43.744 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Server version
number: 9.0.58.0
28-Nov-2023 13:15:43.744 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log OS Name:
 Linux
28-Nov-2023 13:15:43.744 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log OS Version:
 5.15.0-89-generic
28-Nov-2023 13:15:43.745 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Architecture:
 amd64
28-Nov-2023 13:15:43.745 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Java Home:
 /usr/lib/jvm/java-11-openjdk-amd64
28-Nov-2023 13:15:43.745 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log JVM Version:
 11.0.20.1+1-post-Ubuntu-0ubuntu122.04
28-Nov-2023 13:15:43.745 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log JVM Vendor:
 Ubuntu
28-Nov-2023 13:15:43.746 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log CATALINA_BASE:
 /var/lib/tomcat9
28-Nov-2023 13:15:43.746 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log CATALINA_HOME:
 /usr/share/tomcat9
28-Nov-2023 13:15:43.758 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: --add-opens=java.base/java.lang=ALL-UNNAMED
28-Nov-2023 13:15:43.759 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: --add-opens=java.base/java.io <http://java.io>=ALL-UNNAMED
28-Nov-2023 13:15:43.759 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: --add-opens=java.base/java.util=ALL-UNNAMED
28-Nov-2023 13:15:43.760 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: --add-opens=java.base/java.util.concurrent=ALL-UNNAMED
28-Nov-2023 13:15:43.760 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: --add-opens=java.rmi/sun.rmi.transport=ALL-UNNAMED
28-Nov-2023 13:15:43.760 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument:
-Djava.util.logging.config.file=/var/lib/tomcat9/conf/logging.properties
28-Nov-2023 13:15:43.761 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Djava.util.logging.manager=org.apache.juli.ClassLoaderLogManager 
28-Nov-2023 13:15:43.761 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Djava.awt.headless=true
28-Nov-2023 13:15:43.761 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Djdk.tls.ephemeralDHKeySize=2048
28-Nov-2023 13:15:43.761 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Djava.protocol.handler.pkgs=org.apache.catalina.webresources
28-Nov-2023 13:15:43.762 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Dorg.apache.catalina.security.SecurityListener.UMASK=0027
28-Nov-2023 13:15:43.762 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Dignore.endorsed.dirs=
28-Nov-2023 13:15:43.762 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Dcatalina.base=/var/lib/tomcat9
28-Nov-2023 13:15:43.762 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Dcatalina.home=/usr/share/tomcat9
28-Nov-2023 13:15:43.763 INFO [main]
org.apache.catalina.startup.VersionLoggerListener.log Command line
argument: -Djava.io.tmpdir=/tmp
28-Nov-2023 13:15:43.768 INFO [main]
org.apache.catalina.core.AprLifecycleListener.lifecycleEvent Loaded Apache 
Tomcat Native library [1.2.31] using APR version [1.7.0].
28-Nov-2023 13:15:43.769 INFO [main]
org.apache.catalina.core.AprLifecycleListener.lifecycleEvent APR
capabilities: IPv6 [true], sendfile [true], accept filters [false], random 
[true], UDS [true].
28-Nov-2023 13:15:43.771 INFO [main]
org.apache.catalina.core.AprLifecycleListener.lifecycleEvent APR/OpenSSL 
configuration: useAprConnector [false], useOpenSSL [true]
28-Nov-2023 13:15:43.776 INFO [main]
org.apache.catalina.core.AprLifecycleListener.initializeSSL OpenSSL
successfully initialized [OpenSSL 3.0.2 15 Mar 2022]
28-Nov-2023 13:15:44.229 INFO [main]
org.apache.coyote.AbstractProtocol.init Initializing ProtocolHandler
["http-nio-8080"]
28-Nov-2023 13:15:44.268 INFO [main]
org.apache.catalina.startup.Catalina.load Server initialization in [799] 
milliseconds
28-Nov-2023 13:15:44.328 INFO [main]
org.apache.catalina.core.StandardService.startInternal Starting service
[Catalina]
28-Nov-2023 13:15:44.328 INFO [main]
org.apache.catalina.core.StandardEngine.startInternal Starting Servlet
engine: [Apache Tomcat/9.0.58 (Ubuntu)]
28-Nov-2023 13:15:44.345 INFO [main]
org.apache.catalina.startup.HostConfig.deployWAR Deploying web application 
archive [/var/lib/tomcat9/webapps/ROOT.war]
28-Nov-2023 13:15:54.672 INFO [main]
org.apache.jasper.servlet.TldScanner.scanJars At least one JAR was scanned for TLDs yet contained no TLDs. Enable debug logging for this logger for a 
complete list of JARs that were scanned but no TLDs were found in them.
Skipping unneeded JARs during scanning can improve startup time and JSP
compilation time.
28-Nov-2023 13:16:08.279 INFO [main]
org.apache.catalina.startup.HostConfig.deployWAR Deployment of web
application archive [/var/lib/tomcat9/webapps/ROOT.war] has finished in
[23,934] ms
28-Nov-2023 13:16:08.282 INFO [main]
org.apache.coyote.AbstractProtocol.start Starting ProtocolHandler
["http-nio-8080"]
28-Nov-2023 13:16:08.302 INFO [main]
org.apache.catalina.startup.Catalina.start Server startup in [24033]
milliseconds

root@mail:/var/lib/tomcat9/logs# lsof -i :8080
COMMAND   PID   USER   FD   TYPE DEVICE SIZE/OFF NODE NAME
java    58986 tomcat   37u  IPv6 571175      0t0  TCP *:http-alt (LISTEN) 
root@mail:/var/lib/tomcat9/logs#


As a result my frontend server (haproxy) cannot connect to the tomcat9
backend server. What's wrong?



Was there any change in JVM arguments recently?

You can force JVM to use IPv4 by adding following argument:

-Djava.net.preferIPv4Stack=true


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