is a tool to transfer data from or to a server, using one of the supported protocols (DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET and TFTP). The command is designed to work without user interaction.
curl -vkl [host url]
is Arbitrary TCP and UDP connections and listens
nc -vz [ip/url] [port]
The netcat utility can be run in the server mode on a specified port listening for incoming connections
nc -l [port]
is check the listening ports and applications
check for TCP and UDP
netstat -antup
same with netstat
lsof -i -P -n | grep LISTEN