Provided by: afnix_3.8.0-1_amd64 bug

NAME

       net - standard networking module

STANDARD NETWORKING MODULE

       The  Standard Networking module is an original implementation of networking facilities for
       the Internet Protocol. The module features standard TCP and UDP sockets for point to point
       communication  as  well  as  multicast  socket. Numerous functions and objects for address
       manipulation are also included in this module. This module is also designed to support  IP
       version 6 with certain platforms.

       IP address
       The IP based communication uses a standard address to reference a particular peer. With IP
       version 4, the standard dot notation is with 4 bytes. With  IP  version  6,  the  standard
       semicolon notation is with 16 bytes. The current implementation supports both versions.

       127.0.0.1       # ipv4 localhost
       0:0:0:0:0:0:0:1 # ipv6 localhost

       IP  address  architecture and behavior are described in various documents as listed in the
       bibliography.

       Domain name system
       The translation between a host name and an IP address is performed  by  a  resolver  which
       uses   the  Domain  Name  System  or  DNS.  Access  to  the  DNS  is  automatic  with  the
       implementation. Depending on the machine resolver configuration, a particular domain  name
       translation  might result in an IP version 4 or IP version 6 address. Most of the time, an
       IP version 4 address is returned.  The mapping between an  IP  address  and  a  host  name
       returns  the  associated  canonical  name  for that IP address. This is the reverse of the
       preceding operation.

       The Address class
       The Address class allows manipulation of IP address. The constructor takes a string as its
       arguments.  The  argument  string  can be either an IP address or a host name which can be
       qualified or not. When the address is  constructed  with  a  host  name,  the  IP  address
       resolution is done immediately.

       Name to address translation
       The  most  common operation is to translate a host name to its equivalent IP address. Once
       the Address object is constructed, the get-address method returns a string  representation
       of  the internal IP address. The following example prints the IP address of the localhost,
       that is 127.0.0.1 with IP version 4.

       # load network module
       interp:library "afnix-net"
       # get the localhost address
       const addr (afnix:net:Address "localhost")
       # print the ip address
       println (addr:get-address)

       As another example, the get-host-name function  returns  the  host  name  of  the  running
       machine. The previous example can be used to query its IP address.

       Address to name translation
       The reverse operation of name translation maps an IP address to a canonical name. It shall
       be noted that the reverse lookup is not done automatically, unless the reverse flag is set
       in the constructoor. The get-canonical-name method of the Address class returns such name.
       Example XNET001.als is a demonstration program which prints the address original name, the
       IP  address  and  the canonical name. Fell free to use it with your favorite site to check
       the equivalence between the original name and the canonical name.

       # print the ip address information of the arguments
       # usage: axi XNET001.als [hosts ...]
       # get the network module
       interp:library "afnix-net"
       # print the ip address
       const ip-address-info (host) {
         try {
           const addr (afnix:net:Address host true)
           println "host name        : " (addr:get-name)
           println "  ip address     : " (addr:get-address)
           println "  canonical name : " (
             addr:get-canonical-name)
           # get aliases
           const size (addr:get-alias-size)
           loop (trans i 0) (< i size) (i:++) {
             println "  alias address  : " (
               addr:get-alias-address i)
             println "  alias name     : " (
               addr:get-alias-name i)
           }
         } (errorln "error: " what:reason)
       }
       # get the hosts
       for (s) (interp:argv) (ip-address-info s)
       zsh> axi net-0001.als localhost
       host name        : localhost
       ip address     : 127.0.0.1
       canonical name : localhost

       Address operations
       The  Address  class  provides  several  methods  and  operators  that  ease  the   address
       manipulation  in  a  protocol  indepedant  way.  For example, the == operator compares two
       addresses. The ++ operator can also be used to get the next IP address.

       Transport layers
       The two transport layer protocols supported by the Internet protocol is the TCP,  a  full-
       duplex  oriented  protocol, and UDP, a datagram protocol. TCP is a reliable protocol while
       UDP is not. By reliable, we mean that the protocol provides automatically some  mechanisms
       for  error  recovery, message delivery, acknowledgment of reception, etc... The use of TCP
       vs. UDP is dictated mostly by the reliability concerns,  while  UDP  reduces  the  traffic
       congestion.

       Service port
       In the client-server model, a connection is established between two hosts. The connections
       is made via the IP address and the port number. For a given  service,  a  port  identifies
       that  service  at a particular address. This means that multiple services can exist at the
       same address. More precisely, the transport layer protocol is also used to  distinguish  a
       particular  service.  The  network module provides a simple mechanism to retrieve the port
       number, given its name and protocol.  The  function  get-tcp-service  and  get-udp-service
       returns  the  port  number for a given service by name. For example, the daytime server is
       located at port number 13.

       assert 13 (afnix:net:get-tcp-service "daytime")
       assert 13 (afnix:net:get-udp-service "daytime")

       Host and peer
       With the client server model, the only information needed to identify a particular  client
       or  server  is  the  address  and  the port number. When a client connects to a server, it
       specify the port number the server is operating. The client uses a random port number  for
       itself.  When  a  server  is  created,  the port number is used to bind the server to that
       particular port. If the port is already in use, that binding will fail. From  a  reporting
       point  of view, a connection is therefore identified by the running host address and port,
       and the peer address and port. For a client, the peer is the server.  For  a  server,  the
       peer is the client.

       TCP client socket
       The  TcpClient  class creates an TCP client object by address and port. The address can be
       either a string or an Address object. During the object construction,  the  connection  is
       established  with  the  server. Once the connection is established, the client can use the
       read and write method to communicate with the server. The TcpClient class is derived  from
       the Socket class which is derived from the InputStream and OutputStream classes.

       Day time client
       The  simplest  example  is a client socket which communicates with the daytime server. The
       server is normally running on all machines and is located at port 13.

       # get the network module
       interp:library "afnix-net"
       # get the daytime server port
       const port (afnix:net:get-tcp-service "daytime")
       # create a tcp client socket
       const s (afnix:net:TcpClient "localhost" port)
       # read the data - the server close the connection
       while (s:valid-p) (println (s:readln))

       Example 3201.als in the example directory prints the day time of the  local  host  without
       argument  or  the day time of the argument. Feel free to use it with www.afnix.org. If the
       server you are trying to contact does not have a day time server,  an  exception  will  be
       raised and the program terminates.

       zsh> axi 3201.als www.afnix.org

       HTTP request example
       Another example which illustrates the use of the TcpClient object is a simple client which
       download a web page. At this stage we  are  not  concern  with  the  URL  but  rather  the
       mechanics  involved.  The  request  is made by opening a TCP client socket on port 80 (the
       HTTP server port) and sending a request by writing some HTTP commands. When  the  commands
       have  been  sent, the data sent by the server are read and printed on the standard output.
       Note that this example is not concerned by error detection.

       # fetch an html page by host and page
       # usage: axi 3203.als [host] [page]
       # get the network module
       interp:library "afnix-net"
       interp:library "afnix-sys"
       # connect to the http server and issue a request
       const send-http-request (host page) {
         # create a client sock on port 80
         const s     (afnix:net:TcpClient host 80)
         const saddr (s:get-socket-address)
         # format the request
         s:writeln "GET " page " HTTP/1.1"
         s:writeln "Host: " (saddr:get-canonical-name)
         s:writeln "Connection: close"
         s:writeln "User-Agent: afnix tcp client example"
         s:newline
         # write the result
         while (s:valid-p) (println (s:readln))
       }
       # get the argument
       if (!= (interp:argv:length) 2) (afnix:sys:exit 1)
       const host (interp:argv:get 0)
       const page (interp:argv:get 1)
       # send request
       send-http-request host page

       UDP client socket
       UDP client socket is similar to TCP client socket. However, due to the  unreliable  nature
       of  UDP, UDP clients are somehow more difficult to manage. Since there is no flow control,
       it becomes more difficult to assess whether or not a datagram has reached its destination.
       The  same apply for a server, where a reply datagram might be lost. The UdpClient class is
       the class which creates a UDP client object. Its usage is similar to the TcpClient.

       The time client
       The UDP time server normally runs on port 37 is the best place to enable it. A UDP  client
       is created with the UdpClient class. Once the object is created, the client sends an empty
       datagram to the server. The server send a reply datagram with 4  bytes,  in  network  byte
       order,  corresponding  to  the  date  as of January 1st 1900. Example 3204.als prints date
       information after contacting the local host time server or the host specified as the first
       argument.

       # get the libraries
       interp:library "afnix-net"
       interp:library "afnix-sys"
       # get the daytime server port
       const port (afnix:net:get-udp-service "time")
       # create a client socket and read the data
       const print-time (host) {
         # create a udp client socket
         const s (afnix:net:UdpClient host port)
         # send an empty datagram
         s:write
         # read the 4 bytes data and adjust to epoch
         const buf (s:read 4)
         const val (- (buf:get-quad) 2208988800)
         # format the date
         const time (afnix:sys:Time val)
         println (time:format-date) ' ' (time:format-time)
       }
       # check for one argument or use localhost
       const host (if (== (interp:argv:length) 0)
         "localhost" (interp:argv:get 0))
       print-time host

       This  example calls for several comments. First the write method without argument sends an
       empty datagram. It is the datagram which trigger the server. The read method reads 4 bytes
       from the reply datagram and places them in a Buffer object. Since the bytes are in network
       byte order, the conversion into an  integer  value  is  done  with  the  get-quad  method.
       Finally,  in  order  to  use  the Time class those epoch is January 1st 1970, the constant
       2208988800 is subtracted from the result. Remember that the time server sends the date  in
       reference  to  January  1st  1900.  More information about the time server can be found in
       RFC738.

       More on reliability
       The previous example has some inherent problems due to the unreliability of  UDP.  If  the
       first  datagram  is  lost, the read method will block indefinitely. Another scenario which
       causes the read method to block is the loss of the server reply datagram. Both problem can
       generally  be  fixed  by checking the socket with a timeout using the valid-p method. With
       one argument, the method timeout and return false. In this case, a  new  datagram  can  be
       send to the server. Example 3205.als illustrates this point. We print below the extract of
       code.

       # create a client socket and read the data
       const print-time (host) {
         # create a udp client socket
         const s (afnix:net:UdpClient host port)
         # send an empty datagram until the socket is valid
         s:write
         # retransmit datagram each second
         while (not (s:valid-p 1000)) (s:write)
         # read the 4 bytes data and adjust to epoch
         const buf (s:read 4)
         const val (- (buf:get-quad) 2208988800)
         # format the date
         const time (afnix:sys:Time val)
         println (time:format-date) ' ' (time:format-time)
       }

       Note that this solution is a naive one. In the case  of  multiple  datagrams,  a  sequence
       number  must  be placed because there is no clue about the lost datagram. A simple rule of
       thumb is to use TCP as soon as reliability is a concern, but  this  choice  might  not  so
       easy.

       Error detection
       Since  UDP is not reliable, there is no simple solution to detect when a datagram has been
       lost. Even worse, if the server is not running, it is not easy to detect that  the  client
       datagram  has  been  lost.  In such situation, the client might indefinitely send datagram
       without getting an answer. One solution to this problem is again to count  the  number  of
       datagram re-transmit and eventually give up after a certain time.

       Socket class
       The  Socket  class  is the base class for both TcpClient and UdpClient. The class provides
       methods to query the socket port and address as well as the peer port and address. Note at
       this  point  that the UDP socket is a connected socket. Therefore, these methods will work
       fine. The get-socket-address and get-socket-port returns respectively the address and port
       of  the  connected socket. The get-peer-address and get-peer-port returns respectively the
       address and port of the connected socket's peer. Example 3206.als illustrates the  use  of
       these methods.

       # create a client socket and read the data
       const print-socket-info (host) {
         # create a tcp client socket
         const s (afnix:net:TcpClient host port)
         # print socket address and port
         const saddr (s:get-socket-address)
         const sport (s:get-socket-port)
         println "socket ip address     : " (
           saddr:get-address)
         println "socket canonical name : " (
           saddr:get-canonical-name)
         println "socket port           : " sport
         # print peer address and port
         const paddr (s:get-peer-address)
         const pport (s:get-peer-port)
         println "peer ip address       : " (
           paddr:get-address)
         println "peer canonical name   : " (
           paddr:get-canonical-name)
         println "peer port             : " pport
       }

       Socket predicates
       The  Socket class is associated with the socket-p predicate. The respective client objects
       have the tcp-client-p predicate and udp-client-p predicate.

       TCP server socket
       The TcpServer class creates an TCP server object. There are several constructors  for  the
       TCP  server.  In its simplest form, without port, a TCP server is created on the localhost
       with an ephemeral port number (i.e port 0 during the call). With a port  number,  the  TCP
       server  is created on the localhost. For a multi-homed host, the address to use to run the
       server can be specified as the first argument. The address can be either a  string  or  an
       Address  object.  In  both cases, the port is specified as the second argument. Finally, a
       third argument called the backlog can  be  specified  to  set  the  number  of  acceptable
       incoming  connection.  That is the maximum number of pending connection while processing a
       connection. The following example shows various ways to create a TCP server.

       trans s (afnix:net:TcpServer)
       trans s (afnix:net:TcpServer 8000)
       trans s (afnix:net:TcpServer 8000 5)
       trans s (afnix:net:TcpServer "localhost" 8000)
       trans s (afnix:net:TcpServer "localhost" 8000 5)
       trans s (afnix:net:TcpServer (
           Address "localhost") 8000)
       trans s (afnix:net:TcpServer (
           Address "localhost") 8000 5)

       Echo server example
       A simple echo server can be built and tested with the  standard  telnet  application.  The
       application will echo all lines that are typed with the telnet client. The server is bound
       on the port 8000, since ports 0 to 1024 are privileged ports.

       # get the network module
       interp:library "afnix-net"
       # create a tcp server on port 8000
       const srv (afnix:net:TcpServer 8000)
       # wait for a connection
       const s (srv:accept)
       # echo the line until the end
       while (s:valid-p) (s:writeln (s:readln))

       The telnet session is then quite simple. The line hello world is echoed by the server.

       zsh> telnet localhost 8000
       Trying 127.0.0.1...
       Connected to localhost.
       Escape character is '^]'.
       hello world
       ^D

       The accept method
       The previous example illustrates the mechanics of a server. When the  server  is  created,
       the  server is ready to accept connection. The accept method blocks until a client connect
       with the server. When the connection is established, the accept method  returns  a  socket
       object which can be used to read and write data.

       Multiple connections
       One  problem  with the previous example is that the server accepts only one connection. In
       order to accept multiple connection, the accept method must be placed in a loop,  and  the
       server  operation in a thread (There are some situations where a new process might be more
       appropriate than a thread). Example 3302.als illustrates such point.

       # get the network module
       interp:library "afnix-net"
       # this function echo a line from the client
       const echo-server (s) {
         while (s:valid-p) (s:writeln (s:readln))
       }
       # create a tcp server on port 8000
       const srv (afnix:net:TcpServer 8000)
       # wait for a connection
       while true {
         trans s (srv:accept)
         launch  (echo-server s)
       }

       UDP server socket
       The UdpServer class is similar to the TcpServer object, except that there  is  no  backlog
       parameters.  In  its  simplest  form,  the  UDP server is created on the localhost with an
       ephemeral port (i.e port 0). With a port number, the server is created on  the  localhost.
       For  a  multi-homed host, the address used to run the server can be specified as the first
       argument. The address can be either a string or an Address object. In both cases, the port
       is specified as the second argument.

       trans s (afnix:net:UdpServer)
       trans s (afnix:net:UdpServer 8000)
       trans s (afnix:net:UdpServer "localhost" 8000)
       trans s (afnix:net:UdpServer (
           Address "localhost") 8000)

       Echo server example
       The echo server can be revisited to work with udp datagram. The only difference is the use
       of the accept method. For a UDP server, the method return a Datagram object which  can  be
       used to read and write data.

       # get the network module
       interp:library "afnix-net"
       # create a udp server on port 8000
       const srv (afnix:net:UdpServer 8000)
       # wait for a connection
       while true {
         trans dg   (srv:accept)
         dg:writeln (dg:readln)
       }

       Datagram object
       With  a  UDP  server,  the  accept  method  returns  a  Datagram  object. Because a UDP is
       connection-less, the server has no idea from whom the datagram is coming  until  that  one
       has  been  received.  When a datagram arrives, the Datagram object is constructed with the
       peer address being the source address. Standard i/o methods can be used to read or  write.
       When  a  write  method  is  used,  the data are sent back to the peer in a form of another
       datagram.

       # wait for a datagram
       trans dg (s:accept)
       # assert datagram type
       assert true (datagram-p dg)
       # get contents length
       println "datagram buffer size : " (dg:get-buffer-length)
       # read a line from this datagram
       trans line (dg:readln)
       # send it back to the sender
       s:writeln line

       Input data buffer
       For a datagram, and generally speaking,  for  a  UDP  socket,  all  input  operations  are
       buffered.  This  means that when a datagram is received, the accept method places all data
       in an input buffer. This means that a read operation does not necessarily flush the  whole
       buffer  but  rather  consumes  only  the requested character. For example, if one datagram
       contains the string hello world. A call to readln will return the entire string. A call to
       read  will  return  only the character 'h'. Subsequent call will return the next available
       characters. A call like read 5 will return a buffer with 5  characters.  Subsequent  calls
       will  return  the  remaining  string.  In  any case, the get-buffer-length will return the
       number of available characters in the buffer. A call to valid-p will return true if  there
       are  some  characters in the buffer or if a new datagram has arrived. Care should be taken
       with the read method. For example if there is only 4 characters in the input buffer and  a
       call  to  read  for  10  characters is made, the method will block until a new datagram is
       received which can fill the remaining 6 characters. Such situation can be avoided by using
       the  get-buffer-length  and the valid-p methods. Note also that a timeout can be specified
       with the valid-p method.

       Low level socket methods
       Some folks always prefer to do everything  by  themselves.  Most  of  the  time  for  good
       reasons. If this is your case, you might have to use the low level socket methods. Instead
       of using a client or server class, the implementation let's  you  create  a  TcpSocket  or
       UdpSocket.  Once  this done, the bind, connect and other methods can be used to create the
       desired connection.

       A socket client
       A simple TCP socket client is created with the TcpSocket class. Then the connect method is
       called to establish the connection.

       # create an address and a tcp socket
       const addr (afnix:net:Address "localhost")
       const sid  (afnix:net:TcpSocket)
       # connect the socket
       sid:connect 13 addr

       Once the socket is connected, normal read and write operations can be performed. After the
       socket is created, it is possible to set some options. A typical  one  is  NO-DELAY  which
       disable the Naggle algorithm.

       # create an address and a tcp socket
       const addr (afnix:net:Address "localhost")
       const sid  (afnix:net:TcpSocket)
       # disable the naggle algorithm
       sid:set-option sid:NO-DELAY true
       # connect the socket
       sid:connect 13 addr

NETWORKING REFERENCE

       Address
       The  Address  class  is  the Internet address manipulation class. The class can be used to
       perform the conversion between a host name  and  an  IP  address.  The  opposite  is  also
       possible. Finally, the class supports both IP version 4 and IP version 6 address formats.

       Predicate

              address-p

       Inheritance

              Object

       Constructors

              Address (String)
              The Address constructor create an IP address object by name. The name argument is a
              string of a host name or a valid IP address representation.

              Address (String Boolean)
              The Address constructor create an IP address object by name and force  the  reverse
              lookup  resolution  depending  on  the  boolean flag value. The first argument is a
              string of a host name or a valid IP address representation. The second argument  is
              a  boolean  flag that indicates whether or not reverse lookup must occur during the
              construction.

       Operators

              == -> Boolean (Address)
              The == operator returns true  if  the  calling  object  is  equal  to  the  address
              argument.

              != -> Boolean (Address)
              The  !=  operator  returns  true  if the calling object is not equal to the address
              argument.

              < -> Boolean (Address)
              The < operator returns true if the calling address is less than the address object.

              <= -> Boolean (Address)
              The <= operator returns true if the calling address is less equal than the  address
              object.

              > -> Boolean (Address)
              The  >  operator  returns  true  if the calling address is greater than the address
              object.

              >= -> Boolean (Address)
              The <= operator returns true if the calling  address  is  greater  equal  than  the
              address object.

              ++ -> Address (Address)
              The ++ operator increments the calling address by one position.

       Methods

              resolve -> String Boolean (none)
              The  resolve method resolves an host name and eventually performs a reverse lookup.
              The first argument is a string of a host name or a valid IP address representation.
              The  second argument is a boolean flag that indicates whether or not reverse lookup
              must occur during the resolution.

              get-name -> String (none)
              The get-name method returns the original name used during the object construction.

              get-address -> String (none)
              The get-address method returns a string  representation  of  the  IP  address.  The
              string  representation  follows the IP version 4 or IP version 6 preferred formats,
              depending on the internal representation.

              get-vector -> Vector (none)
              The get-vector method returns a vector representation of the IP address. The vector
              result  follows the IP version 4 or IP version 6 preferred format, depending on the
              internal representation.

              get-canonical-name -> String (none)
              The get-canonical-name method returns a fully qualified name of  the  address.  The
              resulting  name  is obtained by performing a reverse lookup. Note that the name can
              be different from the original name.

              get-alias-size -> Integer (none)
              The get-alias-size method returns the number of aliases for the address. The number
              of aliases includes as well the primary resolved name which is located at index 0.

              get-alias-name -> String (Integer)
              The  get-alias-name  method  returns a fully qualified name of the address alias by
              index. The first argument is the alias index number which  must  be  in  the  alias
              index  range.  The  resulting name is obtained by performing a reverse lookup. Note
              that the name can be different from the original name. Using index 0 is  equivalent
              to call get-canonical-name.

              get-alias-address -> String (Integer)
              The  get-alias-address  method  returns  a  string representation of the IP address
              alias by index. The first argument is the alias index number which must be  in  the
              alias index range. The string representation follows the IP version 4 or IP version
              6 preferred formats, depending on the internal representation.  Using  index  0  is
              equivalent to call get-address.

              get-alias-vector -> Vector (Integer)
              The get-alias-vector method returns a vector representation of the IP address alias
              by index. The first argument is the alias index number which must be in  the  alias
              index  range.  The vector result follows the IP version 4 or IP version 6 preferred
              format, depending on the internal representation. Using index 0  is  equivalent  to
              call get-vector.

       Functions

              get-loopback -> String (none)
              The  get-loopback  function  returns  the  name  of the machine loopback. On a UNIX
              system, that name is localhost.

              get-tcp-service -> String (Integer)
              The get-tcp-service function returns the name of the tcp  service  given  its  port
              number. For example, the tcp service at port 13 is the daytime server.

              get-udp-service -> String (Integer)
              The  get-udp-service  function  returns  the name of the udp service given its port
              number. For example, the udp service at port 19 is the chargen server.

       Socket
       The Socket class is  a  base  class  for  the   AFNIX   network  services.  The  class  is
       automatically  constructed  by  a  derived  class  and provide some common methods for all
       socket objects.

       Predicate

              socket-p

       Inheritance

              InputStreamOutputStream

       Constants

              REUSE-ADDRESS
              The REUSE-ADDRESS constant is used  by  the  set-option  method  to  enable  socket
              address  reuse.  This  option  changes the rules that validates the address used by
              bind. It is not recommended to use that option as it decreases TCP reliability.

              BROADCAST
              The BROADCAST constant is used by the set-option  method  to  enable  broadcast  of
              packets.  This  options  only  works  with  IP version 4 address. The argument is a
              boolean flag only.

              DONT-ROUTE
              The DONT-ROUTE constant is used by the set-option method to control if a packet  is
              to be sent via the routing table. This option is rarely used with . The argument is
              a boolean flag only.

              KEEP-ALIVE
              The KEEP-ALIVE constant is used by the set-option method to check  periodically  if
              the  connection is still alive. This option is rarely used with . The argument is a
              boolean flag only.

              LINGER
              The LINGER constant is used by  the  set-option  method  to  turn  on  or  off  the
              lingering  on  close.  If  the  first  argument is true, the second argument is the
              linger time.

              RCV-SIZE
              The RCV-SIZE constant is used by the set-option method to set  the  receive  buffer
              size.

              SND-SIZE
              The SND-SIZE constant is used by the set-option method to set the send buffer size.

              HOP-LIMIT
              The HOP-LIMIT constant is used by the set-option method to set packet hop limit.

              MULTICAST-LOOPBACK
              The MULTICAST-LOOPBACK constant is used by the set-option method to control whether
              or not multicast packets are copied to the loopback. The argument is a boolean flag
              only.

              MULTICAST-HOP-LIMIT
              The  MULTICAST-HOP-LIMIT  constant  is used by the set-option method to set the hop
              limit for multicast packets.

              MAX-SEGMENT-SIZE
              The MAX-SEGMENT-SIZE constant is used by the  set-option  method  to  set  the  TCP
              maximum segment size.

              NO-DELAY
              The  NO-DELAY  constant  is  used by the set-option method to enable or disable the
              Naggle algorithm.

       Methods

              bind -> none (Integer)
              The bind method binds this socket to the port specified as the argument.

              bind -> none (Integer Address)
              The bind method binds this socket to the port specified as the first  argument  and
              the address specified as the second argument.

              connect -> none (Integer Address [Boolean])
              The connect method connects this socket to the port specified as the first argument
              and the address specified as the second argument. A connected socket is useful with
              udp  client that talks only with one fixed server. The optional third argument is a
              boolean flag that permits to select whether or  not  the  alias  addressing  scheme
              should  be  used. If the flag is false, the default address is used. If the flag is
              true, an attempt is made to connect to the first successful address that is part of
              the alias list.

              open-p -> Boolean (none)
              The  open-p  predicate returns true if the socket is open. The method checks that a
              descriptor is attached to the object. This does not mean  that  the  descriptor  is
              valid in the sense that one can read or write on it. This method is useful to check
              if a socket has not been closed.

              shutdown -> Boolean (none|Boolean)
              The shutdown method shutdowns  or  close  the  connection.  Without  argument,  the
              connection  is  closed  without  consideration  for  those  symbols attached to the
              object. With one argument, the connection is closed in one direction only.  If  the
              mode  argument  is  false,  further  receive is disallowed. If the mode argument is
              true, further send is  disallowed.  The  method  returns  true  on  success,  false
              otherwise.

              ipv6-p -> Boolean (none)
              The ipv6-p predicate returns true if the socket address is an IP version 6 address,
              false otherwise.

              get-socket-address -> Address (none)
              The get-socket-address method returns an address object of the socket. The returned
              object can be later used to query the canonical name and the ip address.

              get-socket-port -> Integer (none)
              The get-socket-port method returns the port number of the socket.

              get-socket-authority -> String (none)
              The  get-socket-authority  method  returns  the  authority string in the form of an
              address and port pair of the socket.

              get-peer-address -> Address (none)
              The get-peer-address method returns an address object of  the  socket's  peer.  The
              returned object can be later used to query the canonical name and the ip address.

              get-peer-port -> Integer (none)
              The get-peer-port method returns the port number of the socket's peer.

              get-peer-authority -> String (none)
              The  get-peer-authority  method  returns  the  authority  string  in the form of an
              address and port pair of the socket's peer.

              set-option -> Boolean (constant [Boolean|Integer] [Integer])
              The set-option method set a socket option. The first argument is the option to set.
              The  second  argument  is  a  boolean  value  which  turn on or off the option. The
              optional third argument is an integer needed for some options.

              set-encoding-mode -> none (Item|String)
              The set-encoding-mode method sets the input and output encoding mode. In the  first
              form,  with  an item, the stream encoding mode is set directly. In the second form,
              the encoding mode is set with a string and might also alter the  stream  transcoing
              mode.

              set-input-encoding-mode -> none (Item|String)
              The set-input-encoding-mode method sets the input encoding mode. In the first form,
              with an item, the stream encoding mode is set directly. In  the  second  form,  the
              encoding mode is set with a string and might also alter the stream transcoing mode.

              get-input-encoding-mode -> Item (none)
              The get-input-encoding-mode method return the input encoding mode.

              set-output-encoding-mode -> none (Item|String)
              The  set-output-encoding-mode  method  sets  the output encoding mode. In the first
              form, with an item, the stream encoding mode is set directly. In the  second  form,
              the  encoding  mode is set with a string and might also alter the stream transcoing
              mode.

              get-output-encoding-mode -> Item (none)
              The get-output-encoding-mode method return the output encoding mode.

       TcpSocket
       The TcpSocket class is a base class for all tcp socket objects. The class is derived  from
       the  Socket  class  and provides some specific tcp methods. If a TcpSocket is created, the
       user is responsible to connect it to the proper address and port.

       Predicate

              tcp-socket-p

       Inheritance

              Socket

       Constructors

              TcpSocket (none)
              The TcpSocket constructor creates a new tcp socket.

       Methods

              accept -> TcpSocket (none)
              The accept method waits for incoming connection  and  returns  a  TcpSocket  object
              initialized  with  the connected peer. The result socket can be used to perform i/o
              operations. This method is used by tcp server.

              listen -> Boolean (none|Integer)
              The listen method initialize  a  socket  to  accept  incoming  connection.  Without
              argument,  the default number of incoming connection is 5. The integer argument can
              be used to specify the number of incoming connection  that  socket  is  willing  to
              queue. This method is used by tcp server.

       TcpClient
       The TcpClient class creates a tcp client by host and port. The host argument can be either
       a name or an address object. The  port  argument  is  the  server  port  to  contact.  The
       TcpClient class is derived from the TcpSocket class. This class has no specific methods.

       Predicate

              tcp-client-p

       Inheritance

              TcpSocket

       Constructors

              TcpClient (String Integer)
              The  TcpClient  constructor  creates  a new tcp client socket by host name and port
              number.

       TcpServer
       The TcpServer class creates a tcp server by port. An optional host argument can be  either
       a  name  or an address object. The port argument is the server port to bind. The TcpServer
       class is derived from the TcpSocket class. This class has no specific  methods.  With  one
       argument,  the  server  bind  the  port  argument  on  the  local host. The backlog can be
       specified as the last argument. The host name can also be specified as the first argument,
       the port as second argument and eventually the backlog. Note that the host can be either a
       string or an address object.

       Predicate

              tcp-server-p

       Inheritance

              TcpSocket

       Constructors

              TcpServer (none)
              The TcpServer constructor creates a default tcp server.

              TcpServer (Integer)
              The TcpServer constructor creates a default  tcp  server  which  is  bound  on  the
              specified port argument.

              TcpServer (Integer Integer)
              The  TcpServer  constructor  creates  a  default  tcp  server which is bound on the
              specified port argument. The second argument is the backlog value.

              TcpServer (String Integer)
              The TcpServer constructor creates a tcp server by host name and  port  number.  The
              first argument is the host name. The second argument is the port number.

              TcpServer (String Integer Integer)
              The  TcpServer  constructor  creates a tcp server by host name and port number. The
              first argument is the host name. The second argument is the port number. The  third
              argument is the backlog.

       Datagram
       The  Datagram class is a socket class used by udp socket. A datagram is constructed by the
       UdpSocketaccept method. The purpose of a datagram is to store the peer information so  one
       can  reply  to the sender. The datagram also stores in a buffer the data sent by the peer.
       This class does not have any constructor nor any specific method.

       Predicate

              datagram-p

       Inheritance

              Socket

       UdpSocket
       The UdpSocket class is a base class for all udp socket objects. The class is derived  from
       the Socket class and provides some specific udp methods.

       Predicate

              udp-socket-p

       Inheritance

              Socket

       Constructors

              UdpSocket (none)
              The UdpSocket constructor creates a new udp socket.

       Methods

              accept -> Datagram (none)
              The accept method waits for an incoming datagram and returns a Datagram object. The
              datagram is initialized with the peer address and port  as  well  as  the  incoming
              data.

       UdpClient
       The UdpClient class creates a udp client by host and port. The host argument can be either
       a name or an address object. The  port  argument  is  the  server  port  to  contact.  The
       UdpClient class is derived from the UdpSocket class. This class has no specific methods.

       Predicate

              udp-client-p

       Inheritance

              UdpSocket

       Constructors

              UdpClient (String Integer)
              The  UdpClient  constructor  creates  a  new udp client by host and port. The first
              argument is the host name. The second argument is the port number.

       UdpServer
       The UdpServer class creates a udp server by port. An optional host argument can be  either
       a  name  or an address object. The port argument is the server port to bind. The UdpServer
       class is derived from the UdpSocket class. This class has no specific  methods.  With  one
       argument,  the  server bind the port argument on the local host. The host name can also be
       specified as the first argument, the port as second argument. Note that the  host  can  be
       either a string or an address object.

       Predicate

              udp-server-p

       Inheritance

              UdpSocket

       Constructors

              UdpServer (none)
              The UdpServer constructor creates a default udp server object.

              UdpServer (String|Address)
              The  UdpServer  constructor creates a udp server object by host. The first argument
              is the host name or host address.

              UdpServer (String|Address Integer)
              The UdpServer constructor creates a udp server object by host and port.  The  first
              argument is the host name or host address. The second argument is the port number.

       Multicast
       The  Multicast class creates a udp multicast socket by port. An optional host argument can
       be either a name or an address object. The port argument is the server port to  bind.  The
       Multicast  class  is derived from the UdpSocket class. This class has no specific methods.
       With one argument, the server bind the port argument on the local host. The host name  can
       also  be  specified as the first argument, the port as second argument. Note that the host
       can be either a string or an address object. This class is similar to the UdpServer class,
       except  that  the  socket  join  the  multicast  group  at  construction  and  leave it at
       destruction.

       Predicate

              multicast-p

       Inheritance

              UdpSocket

       Constructors

              Multicast (String|Address)
              The Multicast constructor creates a multicast socket  object  by  host.  The  first
              argument is the host name or host address.

              Multicast (String|Address Integer)
              The  Multicast  constructor creates a multicast socket object by host and port. The
              first argument is the host name or host address. The second argument  is  the  port
              number.