Why Do I Want Networking?
  
   Goal of Networking:  Communication
     Share data
     Pass Messages
  
   Say I want to talk to a friend in Singapore…
     How can I do this?
     What applications and services must I use?
     Where can I access them?
     How will the data get there?
     Will it be reliable?
     Lecture Today…
  
   Motivations for Sockets
  
   What’s in a Socket?
  
   Working with Sockets
  
   Concurrent  Network 
  Applications
  
   Software Engineering for 
  Project 1
     Layered Commuication
        Applicatio           Application           Applicatio
        Applicatio
           n                                          n
           n
        Presentati                                 Presentati
        Presentati                                 Presentati
           on                                         on
           on         End-to-end Transparency         on
         Session                                    Session
         Session                                    Session
        Transport               TC                 Transport
        Transport                P                 Transport
        Network               Network              Network
        Network       IP      Network       IP     Network
        Data Link    802.     Data Link   WiFi     Data Link
        Data Link     3       Data Link            Data Link
         Physical             Physical              Physical
        Physical              Physical             Physical
                           Core Network
            What's really going on…
                                Let’s consider project one…
                                Let’s consider project one…
            Client (mIRC)
            Client (mIRC)                                              Server (IRC)
        128.2.194.242:626                                              Server (IRC)
        128.2.194.242:626                     TCP
                                              TCP                 128.2.237.25:6667
                   2                                              128.2.237.25:6667
                   2
                                   IP            IP           IP           IP 
                 Which             IP            IP           IP           IP 
                                 Packet       Packet        Packet       Packet 
                Is also…         Packet       Packet        Packet       Packet 
                                   #1           #2            #3           #4
                                   #1           #2           #3            #4
                                 Etherne      Etherne      Etherne       Etherne
                 Which          Etherne       Etherne      Etherne      Etherne
                                 t Frame      t Frame      t Frame       t Frame 
                Is also…        t Frame       t Frame      t Frame      t Frame 
                                   #1           #2            #3           #4
                                   #1           #2           #3            #4
       Which is easier?
  
   An application programmer (writing an IRC 
  server)
     Doesn’t need to send IP packets
     Doesn’t need to send Ethernet frames
     Doesn’t need to worry about reliability
     Shouldn’t have to!
  
   Sockets do this!
     TCP streams
     UDP packetized service (Project 2)
  
   You’ll be doing this! (using sockets)
     To share data
     To pass messages