You only have to have his IP adress to find out if he's online.
A succesfull ping means he's online. Though he might (probably?) drop ICMP packets at his firewall.
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You only have to have his IP adress to find out if he's online.
A succesfull ping means he's online. Though he might (probably?) drop ICMP packets at his firewall.
If you only have the MAC and you did not know the IP nor where to look(SomeISP) you would not find them. MACs are not routable. If you know the IP then like el-half says you can ping them and see if they are on line.
IRC or other apps they use may show you the MAC or PC names if both of you our logged onto them.