The mysterious open port 554 tcp on every machine of my network!

Very strange,i have 4 machine,some machines are real hw(slack64 and slackware) one is a phone android,and last is virtual machine. From slack64 to every machine... for i in oracle slackware android;do nmap -p554 -sT -P0 $i;done|grep open 554/tcp open rtsp 554/tcp open rtsp 554/tcp open rtsp I can telnet it from slack64 telnet oracle 554 Trying 192.168.0.21... Connected to oracle. Escape character is '^]'. But if I do ssh to machine..for example oracle.. netstat -na|grep 554 return..empty! Same thing with other machines If I did telnet oracle from oracle.. telnet oracle 554 Trying 192.168.0.21... telnet: connect to address 192.168.0.21: Connection refused What the hell is this? I investigate..very strange.