why my server connect outside tcp113

[songniao]

myserver:apache2+php+mysql+proftpd
i use "netstat -an|grep SYN
it shows:
MyserverIp:40234 OutsideIP1:113 SYN_SEND
MyserverIP:35890 outsideIP2:113 SYN_SEND
MyserverIP:34556 OutsideIP3:113 SYN_SEND
the outside ip seems random.I have no programes to connect outside(113)£¬why?how can i find the programe that connect ouside with 113

[Mit]

Port 113 is ident, are those people users of your FTP? (If so, could it be checking idents)

emerge lsof

then you can use

lsof | grep IPv4

this will show what programs are using what files / resources - more so whats listening than whats connected thou