Connection refused while connecting using ftp

crio-user@manmodesanket:~/workspace/ftp_client$ ftp -p 3.6.128.106 8081
ftp: connect: Connection refused
I was able to successfully connect ftp q-host port
But after restarting the workspace i facing above mentioned issue

@manmodesanket you need to connect to local host
kindly use local host ip address .

Does the ip_address change when we login after some time
I took a break between…now i used new ip_address i am getting
Connected to 15.206.49.240.
500 OOPS: vsftpd: cannot locate user specified in ‘ftp_username’:ftp
ftp> exit