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IP Ports
Problem: When a host receives data from the network, it has no way of knowing what application that data is trying to reach.
Solution: Use IP ports and bind applications to “sockets” (IP:port combinations)
- E.g. any data sent to 128.2.11.43:80 will be handled by CMU's web server.
- Data send to 128.2.11.43:22 will be handled by that machine's SSH daemon
There are 65535 ports.
- 0-1024 are considered “privileged” - only root can bind applications to them
Notes:
Multiple applications cannot bind on the same port (i.e. two different web servers can't be listening on port 80)
For a list of well known port/service mappings, check out the file /etc/services