Sockets Basics

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Sockets Basics

• Conectionless Protocol

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Today

• IPC
• Sockets
• Basic functions
• Handed code
• Q A

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Interprocess Communication

• Mechanism to allow processes to communicate and
  to synchronize their actions
• Within the same system or different systems
• Best provided by messaging systems (no shared
  variables)

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IPC types

• Pipes
• FIFOs
• Streams and messages
• Message queues, semaphores and shared memory
  (system V)
• Sockets and TLI

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Sockets

• Communication among processes in the same system
  (pipes) and different systems
• Characteristics
• Unique address
• Domain dependent
• Types
• Stream
• Sequenced
• Datagram
• Raw
• Connectionless Vs connection oriented

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Connectionless Oriented
Server
Client
Socket
Socket
Bind
Bind
recvfrom
Blocks until data received from a client
sendto
Process request
sendto
recvfrom
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Basic functions

• socket (int family, int type, int protocol)
  defines the socket
• Address family UNIX, internet, Xerox NS, IMP
• Type stream, datagram, raw, sequenced
• Protocol argument specify protocol (tcp, udp,
  icmp, etc)
• Returns a socket file descriptor

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Basic functions cont

• Bind (int sockfd, struct sockaddr myaddr, int
  addrlen) assigns a name to an unnamed socket
  (this is my adddress and any messages received
  for this address are to be given to me)
• sockfd socket file descriptor
• struct sockaddr protocol specific address
  (family, port, address - netid)
• addrlen size of the structure
• returns error if so

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Basic functions cont

• sendto (int sockfd, char buff, int nbytes, int
  flags, struct sockaddr to, int addrlen) send
  message
• recvfrom (int sockfd, char buff, int nbytes, int
  flags, struct sockaddr to, int addrlen)
  receive message
• buff message
• nbytes length of the message

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Handed code

• Init_socket
• send_packet
• receive_packet
• get_addr_byname

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Questions and Answers