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Network Programming

Network Programming. All networked computers have an IP Address Unique In the form of xxx.xxx.xxx.xxx (255.255.255.255) 32 bits = ~4 billion possibilities (IPv4) Most computers have multiple network cards called “interfaces” Wireless card Ethernet adapter VPN. From the cmd. Ports.

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Network Programming

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  1. Network Programming • All networked computers have an IP Address • Unique • In the form of xxx.xxx.xxx.xxx (255.255.255.255) • 32 bits = ~4 billion possibilities (IPv4) • Most computers have multiple network cards called “interfaces” • Wireless card • Ethernet adapter • VPN

  2. From the cmd

  3. Ports • Machine can specify one of ~65K ports • Allows for multiple network connections • First 1024 are reserved by the OS • Common ports • 21 FTP (File Transfer Protocol) • 22 SSH (Secure Shell) • 23 Telnet • 25 SMTP (Simple Mail Transfer Protocol) • 80 HTTP (HyperText Transfer Protocol) • 110 POP3 (Post Office Protocol) ** 13 is Time Protocol and 17 is Quote of the Day

  4. DNS • Domain Name Service • Translates human-readable into IP Address • Relieves burden of memorization! • This is what many applications use • Example: • www.google.com • 74.125.47.106

  5. nslookup

  6. Client/Server • Servers wait – a LOT • Client wants some data/service from server • Process • Client connects to server • Client sends request for info • Server finds the information • Server sends the information • Client/Server disconnect?

  7. “One-shot” Servers

  8. “One-shot” Servers Gee, I’m lonely I need a texture!

  9. “One-shot” Servers Someone loves me! Make a connection

  10. “One-shot” Servers Let me find that for you… GET spriteSheet.png

  11. “One-shot” Servers Here ya go! <DATA>

  12. “One-shot” Servers Gee, I’m lonely

  13. “Broadcast” Servers A B C

  14. “Broadcast” Servers A B C One thread per client

  15. “Broadcast” Servers Here are my coordinates! A <375.0, -41.0> B C

  16. “Broadcast” Servers Hey guys! “A” has moved A “A” is at <375.0, -41.0> B “A” is at <375.0, -41.0> C

  17. Summary • IP Address • Port • Client/Server relationship • Programming: • If you can read/write to files, you can read/write to the network • Developing “Poor Man’s Web Browser” • Developing “Poor Man’s Web Server”

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