There’s a protected service running on the server at arraylist.dhavalkapil.com:9999

java -javaagent:notsoserial-modified.jar -jar server.jar

Can you find the flag in flag.txt in the same directory?

Files:
notsoserial-modified.jar
https://github.com/DhavalKapil/notsoserial
client.jar

java -jar client.jar arraylist.dhavalkapil.com 9999