Common TCP and UDP Ports - CompTIA A+ 220-801: 2.4

TCP (Transmission Control Protocol)

• Connection-oriented
• Reliable delivery
• Can manage out of order messages or retransmissions
• Loads and unloads the moving truck
• Checks for out of order or missing cargo

UDP- User Datagram Protocol 

• Connectionless
• Unreliable
• No reordering of data or retransmissions
• Loads and unloads the moving truck
• Doesn't care about out of order cargo or missing cargo

Ports in a storm of protocols

• IPv4 with TCP/UDP
• Server IP address, server application port number
• Client IP address, client port number
• Non-ephemeral ports- permanent port numbers
• Usually on a server or service

• Ephemeral ports- temporary port numbers
• Determined in real-time by the client workstation 

About port numbers...

• TCP and UDP ports can be any number between 0 and 65,535
• Most servers (services) use non-ephemeral port numbers
• This isn't always the case
• It's just a number
• Port numbers are for communication, not security
• Service port numbers need to be "well known"
• TCP port numbers aren't the same as UDP port numbers

A network connection

TCP ports

• FTP- File Transfer Protocol- tcp/20 (data), tcp/21 (control)
• Telnet- tcp/23
• SMTP- Simple Mail Transfer Protocol- tcp/25
• DNS- Domain Name Services- tcp/53 (zone transfers)
• HTTP- Hypertext Transfer Protocol- tcp/80
• POP3- Post Office Protocol version 3- tcp/110
• IMAP- Internet Message Access Protocol v4- tcp/143
• HTTPS- Hypertext Transfer Protocol Secure- tcp/443
• RDP- Remote Desktop Protocol- tcp/3389

UDP ports

• DNS- Domain Name Services
• udp/5 (queries)