IP(3)                                                       IP(3)

     NAME
          ip - TCP, UDP, IL network protocols over IP

     SYNOPSIS
          bind -a #Itcp /net
          bind -a #Iudp /net
          bind -a #Iil /net

          #Itcp/tcp/clone
          #Itcp/tcp/[0-7]
          #Itcp/tcp/[0-7]/data
          #Itcp/tcp/[0-7]/ctl
          #Itcp/tcp/[0-7]/local
          #Itcp/tcp/[0-7]/remote
          #Itcp/tcp/[0-7]/status
          #Itcp/tcp/[0-7]/listen
          ...

     DESCRIPTION
          The IP device provides the interface for several protocols
          that run over IP on an Ethernet.  TCP and UDP provide the
          standard Internet protocols for reliable stream and unreli-
          able datagram communication.  IL provides a reliable data-
          gram service for communication between Plan 9 machines.  IL
          is the protocol of choice for most Plan 9 services.

          Each of the protocols is served by the IP device, which rep-
          resents each connection by a set of device files.  The top
          level directory of each protocol contains a clone file and
          subdirectories numbered from zero to the number of connec-
          tions configured for this protocol.

          Opening the clone file reserves a connection.  The file
          descriptor returned from the open(2) will point to the con-
          trol file, ctl, of the newly allocated connection.  Reading
          the ctl file returns a text string representing the number
          of the connection.  Connections may be used either to listen
          for incoming calls or to initiate calls to other machines.

          A connection is controlled by writing text strings to the
          associated ctl file.  After a connection has been estab-
          lished data may be read from and written to the data file.
          For the datagram services, IL and UDP, a read of less than
          the length of a datagram will cause the entire datagram to
          be consumed.  Each write to the data file will send a single
          datagram on the network.  The TCP protocol provides a stream
          connection that does not preserve read/write boundaries.

          Prior to sending data remote and local addresses must be set
          for the connection.  For outgoing calls the local port

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     IP(3)                                                       IP(3)

          number will be allocated randomly if none is set.  Addresses
          are set by writing control messages to the ctl file of the
          connection.  The connection is not established until the
          data file is opened.  For IL and TCP the process will block
          until the remote host has acknowledged the connection.  UDP
          opens always succeed.

          The following control messages are supported:

          connect ipaddress!port[!r]
               Set the remote IP address and port number for the con-
               nection.  If the r flag is supplied and no local
               address has been specified the system will allocate a
               restricted port number (less than 1024) for the connec-
               tion to allow communication with Unix machines
               login/exec services.

          disconnect
               (UDP only.)  Clear the remote address of a UDP connec-
               tion.

          announce port
               Set the local address to port. The local IP address can
               not be set.

          backlog n
               (IL and TCP only.)  Set the maximum number of pending
               requests for a given service to n. By default n is set
               to five.  If more than n connections are pending fur-
               ther requests for a service will be rejected.

          Port numbers must be in the range 1 to 32767.  If a local
          port has not been announced prior to a connect a local port
          number will be allocated automatically.  Local ports are
          allocated from 5000 up.

          Several files report the status of a connection.  The remote
          and local files contain the IP address and port number for
          the remote and local side of the connection.  The status
          file contains protocol-dependent information to help debug
          network connections.

          A process may accept incoming connections by calling open on
          the listen file.  The open will block until a new connection
          request arrives.  Then open will return an open file
          descriptor which points to the control file of the newly
          accepted connection.  This procedure will accept all calls
          for the given protocol.

     SEE ALSO
          listen(8), dial(2), ndb(6)

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