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
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
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...