http://www.iana.org/assignments/port-numbers Heh, now study the TCP/IP protocols on the ports you have questions about. No port is reserved for a trojan. A trojan may use a specific port but when the brain trust developed TCP/IP protocol suit they did not say lets reserve port XXXX for a trojan
commplex-main 5000/tcp
commplex-main 5000/udp
Looks like port 5000 can be used with TCP or UDP
RFC 739 TCP(TRANSMISSION CONTROL PROTOCOL)
ftp://ftp.rfc-editor.org/in-notes/rfc793.txt RFC 768 UDP(User Datagram Protocol)
ftp://ftp.rfc-editor.org/in-notes/rfc768.txt Think of TCP and UDP as similar but different protocols. Also study the OSI modle. Here is a basic TCP/IP protocol stack in relation to the OSI model
![[Linked Image]](http://www.protocols.com/pbook/images/tcpipmap.gif)
As you can see both UDP and TCP are on the transport layer of the OSI modle. This is because they are both used for transport. Read and understand what I just gave you and you will have better questions to ask.
If you want to learn to network security.. Study the TCP/IP prtocol stack. Everything you do in a network involves at least several protocols. Learn how the work. How networking in general works. What each layer of the OSI modle describes. How the TCP/IP modle stack is laid out *When authentication starts* Oh and here is where number systems come in handy...