TCP Flashcards
UDP
User Data Cram Protocol
A connectionless protocol. You just set a destination and send data. Does not use handshake
Socket
The instantiation of an end-point in a potential TCP connection
Instantiation
The actual implementation of something defined elsewhere
TCP Socket States
(Most common)
- Listen
- SYN_SENT
- SYN_RECEIVED
- Established
- FIN_WAIT
- CLOSE_WAIT
- CLOSED
Listen
A TCP Socket is ready and listening for incoming connections
(Only seen on the server side)
SYN_SENT
A synchronization request has been sent, but the connection hasn’t been established yet
(Seen on client side)
SYN_RECEIVED
A socket previously in a Listen state has received a synchronization request and sent a SYN/ACK back
(Seen on server side)
Established
The TCP connection is in working order and both sides are free to send each other data
(Seen on both sides)
FIN_WAIT
A FIN has has been sent, but the corresponding ACK from the other end hasn’t been received yet
CLOSE_WAIT
The connection has been closed at the TCP layer, but the application that opened the socket hasn’t released its hold on a socket yet.
CLOSED
The connection has been fully terminated and that no further communicate is possible
Connection-oriented protocol
Establishes a connection and uses this to ensure that all data has been properly transmitted
3 kinds of ports
- System ports
- User ports
- Ephemeral ports
Firewall
A device that blocks traffic that meets certain criteria
