DXARTS 472

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DXARTS 472

• Lecture 10 Network Software

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Computer Networking

• Computer networking can be defined as
  communications between two or more computers.
• Using the Arudino and Processing, you are already
  familiar with one type of computer networking
  RS-232 communications.
• RS-232 is relatively slow, serial and operates
  over short distances -- 15 - 50m max.
• It is a standard that is incorporated into many
  electronic devices -- sensors, computers,
  displays, etc.

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Network Protocols TCP/IP

• In order to communicate over larger distances --
  computer to computer -- we typically use either
  TCP/IP or UDP
• TCP/IP (Transmission Control Protocol/Internet
  Protocol) is a core protocol for Internet
  communications.
• www
• E-mail
• ssh
• We use it to allow different machines to run
  applications that can connect to each other, and
  exchange streams of data.
• An application will communicate with TCP, which
  formats data for sending. TCP sends the formatted
  data up the stack to the IP for transmission to
  the other computer.
• The TCP gives each transmission a sequence
  number, and sends an acknowledgement for any
  received message. This way, both computers TCP
  modules can confirm receipt of whatever data they
  send.
• This makes TCP/IP robust and reliable, capable of
  recognizing when packets of data are lost or
  damaged.

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Network Protocols UDP

• UDP (user datagram protocol) is a simplified
  version of TCP/IP that sends short datagrams
• It does not authenticate and verify the arrival
  of data packets, making it quicker but less
  reliable than TCP/IP
• Messages sent via UDP will not necessarily arrive
  in the order they are sent
• This makes it well suited for fast, lightweight
  applications, such as microcontroller
  communication, real time audio, online games,
  etc.

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Network Ports

• In both TCP/IP and UDP, we send data packets to
  specific port addresses on remote computers.
• This way, different kinds of data can be sent to
  the same machine simultaneously.
• We use a 16-bit number (1-65535), that is agreed
  in advance between the sending and receiving
  machine.
• Certain port numbers are reserved
• FTP(21)
• Telnet(23)
• SMTP(25)
• HTTP(80)
• Typically ports 1-1023 require authorization to
  use

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Routing

• When packets are sent using TCP/IP or UDP, we can
  select a range of different paths for them to
  follow.
• Anycast
• one-to-many message is sent to one of several
  possible addresses
• Broadcast
• one-to-many message is sent all available
  addresses simultaneously
• Multicast
• one-to-many message is sent to a range of
  addresses simultaneously
• Unicast
• one-to-one message is sent to one specific
  address

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OpenSound Control (OSC)

• Developed at Center for New Music and Audio
  Technologies (CNMAT), UC Berkeley.
• OSC is a protocol for communication between
  computers, sound synthesizers and multimedia
  devices, particularly audio-related.
• connect sensors to musical instruments
• receive data from several performers
  simultaneously
• networked performances
• Ported to many software platforms, including
  Processing, MAX/MSP, Python, etc.

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OSC in Processing

• Typically OSC messages are sent between computers
  using UDP.
• In Processing, we can use the oscP5 library
• http//www.sojamo.de/iv/index.php?n11
• OSC messages consist of an address in the format
  /bob, followed by type identifiers i
  (integer), f (float), s (string), etc.
• /bob, f, 0.2

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Lab Exercise

• Work with a partner to establish an OSC
  connection between your computers.
• Write Processing code that makes an event occur
  remotely on each others machine
• Experiment with communicating with other groups,
  arduinos, etc.