Hello
On 2023-01-31 16:05, Haines Brown wrote:
I have an application that refuses to start because its port is
blocked. But I have difficulty knowing what port it is
$ java -jar /usr/local/share/JabRef/JabRef-3.2.jar &
[1] 4831
haines@lenin:~$ Jan 31, 2023 8:36:39 AM
net.sf.jabref.logic.remote.server.Remote
ListenerServerLifecycle open
WARNING: Port is blocked
java.net.BindException: Address already in use
at java.base/sun.nio.ch.Net.bind0(Native Method)
at java.base/sun.nio.ch.Net.bind(Net.java:555)
at java.base/sun.nio.ch.Net.bind(Net.java:544)
at
java.base/sun.nio.ch.NioSocketImpl.bind(NioSocketImpl.java:643)
at java.base/java.net.ServerSocket.bind(ServerSocket.java:388)
at
java.base/java.net.ServerSocket.<init>(ServerSocket.java:274)
at
net.sf.jabref.logic.remote.server.RemoteListenerServer.<init>(RemoteListenerServer.java:40)
at
net.sf.jabref.logic.remote.server.RemoteListenerServerThread.<init>(RemoteListenerServerThread.java:33)
at
net.sf.jabref.logic.remote.server.RemoteListenerServerLifecycle.open(RemoteListenerServerLifecycle.java:41)
at net.sf.jabref.JabRef.start(JabRef.java:137)
at net.sf.jabref.JabRefMain.main(JabRefMain.java:8)
Arguments passed on to running JabRef instance. Shutting down.
How do I know from this what port the java application tried to use?
I try:
$ strings $(which jabref) | wc -l
56
So I try:
$ sudo ss -pt state listening 'sport = :56'
Recv-Q Send-Q Local Address:Port Peer Address:Port Process
This seems a null return. Dores this mean jabref is not using port
56?
If ss, or lsof, or any other tool that shows used ports doesn't show
port 56 being used. Then it's not being used. Or in your case, since
you're filtering ss output to only listening TCP ports, IF it being
used, it might be on a different state that "listening".
Or it could be UDP, but I'm assuming you except jabref to use a TCP
port, thus the use of '-t' option (Disclaimer, I don't what protocols
jabref uses)
However I'm not sure what makes you think jabref is trying to use
(either TCP or UDP) port 56. It your example you didn't show or tell
what to tried to determine it's supposed to use that specific port. wc
-l counts lines and have nothing to do with port numbers. So
$ command | wc -l
Returns the number of lines outputted by "command" (whatever before
pipe). In your case, "strings $(which jabref)" outputs 56 lines.
"sudo lsof -i" as a sudoer user, or "lsof -i" as root (elevated
privileges required to trace used ports) should list processes/commands
using ports, for both listening and established.
OR just "sudo ss -pt state listening" without specifying a source port
to see all the listening port to use used ports, then compare it to
'whatever port number' jabref's documentations says the software uses.
Also, starting jabref with strace, using the network filter, something
like "sudo strace -f -e trace=network
$InsertHereWhateverCommandYouUseToStartJabref", should help you to see
what port it's trying to use.
