Chapter 14 - The Socket Programming Interface

1. Development of the Socket Programming Interface
   1. TCP/IP API is portable (across OS and hardware platforms) and language-independent (C, Java)
   2. API - interface between an application program and the communication protocol in an operating system
   3. follows the UNIX I/O System [open-read-write-close system] using pielines
   4. TCP/IP uses a socket number to uniquely identify the connection

2. Socket Services
   • 3 types of socket interfaces
     • TCP stream communications
     • UDP datagram communications
     • raw datagram
   • six basic communications commands
     • open - establish a socket
     • send - send data to a socket
     • receive - receives data from a socket
     • status - obtains status info about a socket
     • close - terminates a connection
     • abort - cancels an operation and terminates the connection
   • Transmission Control Block (TCB) - data structures that contains details about a connection
   • Creating a Socket function call - socket(family, type, protocol)
     • family - TCP/IP (AF_INET), AppletTalk (AF_APPLETALK), UNIX (AF_UNIX)
     • type - SOCK_STREAM, SOCK_DGRAM, SOCK_RAW
     • protocol
   • Binding a Socket function call - bind(socket, local_address, address_length)
   • Connecting to the Destination - connect(socket, destination_address, address_length)
   • The open Command

     Type	Input	Output
     Unspecified passive open	local port optional: timeout, precedence, security, maximum segment length	Local connection name
     Fully specified passive open	local port, remote IP address, remote port Optional: timeout, precedence, security, maximum segment length	Local connection name
     Active open	local port, destination IP address, destination port Optional: timeout, precedence, security, maximum segment length	Local connection name

   • Sending Data
     • send( socket, buffer_address, length, flags)
     • sendto( socket, buffer_address, length, flags, destination, address_length)
     • sendmsg(socket, message_structure, flags)
     • write(socket, buffer_address, length)
     • writev(socket, iovector, length)
   • Receiving Data
     • read( socket, buffer, length)
     • readv(socket, iovector, length)
     • recv( socket, buffer_address, length, flags)
     • recvmsg(socket, message_structure, flags)
     • recvfrom(socket, buffer_address, length, flags, source_address, address_length)
   • Server Listening
     • listen(socket, queue_length)
     • accept(socket, address, length)
   • Getting Status Information [read from the TCB]
     1. getsockopt(socket, level, option_id, option_result, length)
     2. getpeername(socket, destination_address, address_length)
     3. getsockname(socket, local_address, address_length)
     4. sethostname(name, length)
     5. gethostname(name, length)
     6. setdomainname(name, length)
     7. getdomainname(name, length)
   • Closing a Connection - close(socket)
   • Aborting a Connection - close()
   • UNIX Forks / threads
     • fork creates a copy of the existing application as a new process and starts executing it
     • exec
     • Each new thread that is created inherits a copy of all open sockets from the thread that created it.

Network Programming in Java