






                          XX TTrraannssppoorrtt IInntteerrffaaccee

       Copyright (c) 1993, 1994 NCR Corporation - Dayton, Ohio, USA

       All Rights Reserved

       Permission  to  use,  copy,  modify,  and  distribute   this
       software  and  its documentation for any purpose and without
       fee is hereby granted, provided  that  the  above  copyright
       notice  appear  in  all  copies and that both that copyright
       notice and  this  permission  notice  appear  in  supporting
       documentation,  and  that  the  name  NCR  not  be  used  in
       advertising or publicity pertaining to distribution  of  the
       software  without  specific,  written prior permission.  NCR
       makes no  representations  about  the  suitability  of  this
       software  for  any  purpose.  It is provided "as is" without
       express or implied warranty.

       NCR DISCLAIM ALL WARRANTIES WITH REGARD  TO  THIS  SOFTWARE,
       INCLUDING  ALL  IMPLIED  WARRANTIES  OF  MERCHANTABILITY AND
       FITNESS, IN NO EVENT SHALL NCR BE LIABLE  FOR  ANY  SPECIAL,
       INDIRECT  OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES WHATSOEVER
       RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER  IN  AN
       ACTION  OF  CONTRACT,  NEGLIGENCE  OR OTHER TORTIOUS ACTION,
       ARISING OUT OF OR IN CONNECTION WITH THE USE OR  PERFORMANCE
       OF THIS SOFTWARE.

       Copyright 1993, 1994 X Consortium

       Permission  is hereby granted, free of charge, to any person
       obtaining  a  copy   of   this   software   and   associated
       documentation  files  (the  ``Software''),  to  deal  in the
       Software without restriction, including  without  limitation
       the rights to use, copy, modify, merge, publish, distribute,
       sublicense, and/or sell  copies  of  the  Software,  and  to
       permit  persons  to whom the Software is furnished to do so,
       subject to the following conditions:

       The above copyright notice and this permission notice  shall
       be  included  in  all  copies or substantial portions of the
       Software.

       THE SOFTWARE IS PROVIDED ``AS IS'', WITHOUT WARRANTY OF  ANY
       KIND,  EXPRESS  OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE
       WARRANTIES OF  MERCHANTABILITY,  FITNESS  FOR  A  PARTICULAR
       PURPOSE  AND  NONINFRINGEMENT.   IN  NO  EVENT  SHALL  THE X
       CONSORTIUM  BE  LIABLE  FOR  ANY  CLAIM,  DAMAGES  OR  OTHER
       LIABILITY,  WHETHER  IN  AN  ACTION  OF  CONTRACT,  TORT  OR
       OTHERWISE, ARISING FROM, OUT OF OR IN  CONNECTION  WITH  THE
       SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

       Except  as  contained  in  this  notice,  the  name of the X
       Consortium shall not be used in advertising or otherwise  to
       promote  the  sale,  use  or other dealings in this Software












       without prior written authorization from the X Consortium.

       X Window System is a trademark of X Consortium, Inc.

       Designed by Stuart Anderson (NCR) with help from  Ralph  Mor
       (X Consortium)

                            _D_r_a_f_t _V_e_r_s_i_o_n _0_._6

       NOTE:  This  documentation  does  not  completely  match the
       implementation in R6 (as a result of some late changes  made
       in  the  code).   Specifically,  support  was added for font
       server cloning, and conditional compliation  was  introduced
       for client vs. server code.




















































       _1_.  _P_u_r_p_o_s_e_s _a_n_d _G_o_a_l_s

       The  X Transport Interface is intended to combine all system
       and transport specific code  into  a  single  place  in  the
       source  tree.  This  API  should  be  used by all libraries,
       clients and servers of the X Window System. Use of this  API
       should  allow  the  addition  of new types of transports and
       support for new platforms without making any changes to  the
       source except in the X Transport Interface code.

       This  interface  should solve the problem of multiple #ifdef
       TRANSPORT   and   #ifdef   PLATFORM   statements   scattered
       throughout the source tree.

       This   interface  should  provide  enough  functionality  to
       support  all  types  of  protocols,   including   connection
       oriented  protocols  such as X11 and FS, and connection-less
       oriented protocols such as XDMCP.


       _2_.  _O_v_e_r_v_i_e_w _o_f _t_h_e _i_n_t_e_r_f_a_c_e

       The interface provides an API for use by  applications.  The
       functions  in  this  API  perform work that is common to all
       transports and systems, such as parsing an  address  into  a
       host  and  port  number.  The  functions  in  this  API call
       transport specific functions that are contained in  a  table
       whose  contents  are  defined  at  compile  time. This table
       contains an entry for each type of transport. Each entry  is
       a   record  containing  mostly  pointers  to  function  that
       implements the interface for the given transport.

       This API does not provide an  abstraction  for  select()  or
       poll().     These    function   are   themselves   transport
       independent, so an additional interface is  not  needed  for
       these  functions.   It is also unclear how such an interface
       would affect performance.


       _3_.  _D_e_f_i_n_i_t_i_o_n _o_f _A_d_d_r_e_s_s _S_p_e_c_i_f_i_c_a_t_i_o_n _F_o_r_m_a_t

       Addresses are specified in the following syntax,

       _p_r_o_t_o_c_o_l_/_h_o_s_t_:_p_o_r_t

       where _p_r_o_t_o_c_o_l specifies a protocol family or an alias for a
       protocol family. A definition of common protocol families is
       given in a later section.

       The _h_o_s_t  part  specifies  the  name  of  a  host  or  other
       transport  dependent  entity  that could be interpreted as a
       Network Service Access Point (NSAP).

       The _p_o_r_t part specifies the  name  of  a  Transport  Service












       Access  Point  (TSAP).  The format of the TSAP is defined by
       the  underlying  transport   implementation,   but   it   is
       represented  using  a  string  format  when it is part of an
       address.


       _4_.  _I_n_t_e_r_n_a_l _D_a_t_a _S_t_r_u_c_t_u_r_e_s

       There are two major  data  structures  associated  with  the
       transport independent portion of this interface.  Additional
       data structures may be used internally by each transport.

       _4_._1  _X_t_r_a_n_s_p_o_r_t

       Each transport supported  has  an  entry  in  the  transport
       table.   The  transport  table  is  an  array  of _X_t_r_a_n_s_p_o_r_t
       records. Each record contains all the  entry  points  for  a
       single transport. This record is defined as:
















































       typedef struct _Xtransport {

           char *TransName;
           int  flags;

           XtransConnInfo (*OpenCOTSClient)(
            struct _Xtransport *,    /* transport */
            char *,             /* protocol */
            char *,             /* host */
            char *              /* port */
           );

           XtransConnInfo (*OpenCOTSServer)(
            struct _Xtransport *,    /* transport */
            char *,             /* protocol */
            char *,             /* host */
            char *              /* port */
           );

           XtransConnInfo (*OpenCLTSClient)(
            struct _Xtransport *,    /* transport */
            char *,             /* protocol */
            char *,             /* host */
            char *              /* port */
           );

           XtransConnInfo (*OpenCLTSServer)(
            struct _Xtransport *,    /* transport */
            char *,             /* protocol */
            char *,             /* host */
            char *              /* port */
           );

           int   (*SetOption)(
            XtransConnInfo,          /* connection */
            int,           /* option */
            int            /* arg */
           );

           int   (*CreateListener)(
            XtransConnInfo,          /* connection */
            char *              /* port */
           );

           int   (*ResetListener)(
            XtransConnInfo      /* connection */
           );

           XtransConnInfo (*Accept)(
            XtransConnInfo      /* connection */
           );

           int   (*Connect)(
            XtransConnInfo,          /* connection */












            char *,             /* host */
            char *              /* port */
           );

           int   (*BytesReadable)(
            XtransConnInfo,          /* connection */
            BytesReadable_t *   /* pend */
           );

           int   (*Read)(
            XtransConnInfo,          /* connection */
            char *,             /* buf */
            int            /* size */
           );

           int   (*Write)(
            XtransConnInfo,          /* connection */
            char *,             /* buf */
            int            /* size */
           );

           int   (*Readv)(
            XtransConnInfo,          /* connection */
            struct iovec *,          /* buf */
            int            /* size */
           );

           int   (*Writev)(
            XtransConnInfo,          /* connection */
            struct iovec *,          /* buf */
            int            /* size */
           );

           int   (*Disconnect)(
            XtransConnInfo      /* connection */
           );

           int   (*Close)(
            XtransConnInfo      /* connection */
           );

       } Xtransport;



       The _f_l_a_g_s field can contain an OR of the following masks:

       _T_R_A_N_S___A_L_I_A_S:  indicates  that  this  record  is providing an
       alias, and should not be used to create a listner.

       _T_R_A_N_S___L_O_C_A_L: indicates that this is a LOCALCONN transport.















       _4_._2  _X_t_r_a_n_s_C_o_n_n_I_n_f_o

       Each connection will have an opaque _X_t_r_a_n_s_C_o_n_n_I_n_f_o transport
       connection  object  allocated  for  it. This record contains
       information  specific  to  the  connection.  The  record  is
       defined as:

       typedef struct _XtransConnInfo *XtransConnInfo;

       struct _XtransConnInfo {
           struct _Xtransport     *transptr;
           char  *priv;
           int        flags;
           int        fd;
           int        family;
           char  *addr;
           int        addrlen;
           char  *peeraddr;
           int        peeraddrlen;
       };



       _5_.  _E_x_p_o_s_e_d _T_r_a_n_s_p_o_r_t _I_n_d_e_p_e_n_d_e_n_t _A_P_I

       This  API  is  included in each library and server that uses
       it. The API may be used by the library, but it is not  added
       to  the  public  API  for  that  library.  This interface is
       simply an implementation facilitator. This  API  contains  a
       low  level  set  of  core  primitives,  and  a  few  utility
       functions that are built  on  top  of  the  primitives.  The
       utility functions exist to provide a more familiar interface
       that can be used to port existing code.

       A macro is defined in Xtrans.h for TRANS(func) that  creates
       a  unique  function  name  depending  on  where  the code is
       compiled.   For    example,    when    built    for    Xlib,
       TRANS(OpenCOTSClient) becomes _X11TransOpenCOTSClient.

       All failures are considered fatal, and the connection should
       be closed and re-established  if  desired.  In  most  cases,
       however,  the value of errno will be available for debugging
       purposes.

       _5_._1  _C_o_r_e _I_n_t_e_r_f_a_c_e _A_P_I

          +o XtransConnInfo TRANS(OpenCOTSClient)(char *address)

            This function creates a  Connection-Oriented  Transport
            that  is  suitable  for use by a client.  The parameter
            _a_d_d_r_e_s_s contains the full  address  of  the  server  to
            which  this endpoint will be connected.  This functions
            returns  an  opaque  transport  connection  object   on
            success, or NULL on failure.












          +o XtransConnInfo TRANS(OpenCOTSServer)(char *address)

            This  function  creates a Connection-Oriented Transport
            that is suitable for use by a  server.   The  parameter
            _a_d_d_r_e_s_s  contains the full address to which this server
            will  be  bound.   This  functions  returns  an  opaque
            transport  connection  object  on  success,  or NULL on
            failure.

          +o XtransConnInfo TRANS(OpenCLTSClient)(char *address)

            This function creates a Connection-Less Transport  that
            is suitable for use by a client.  The parameter _a_d_d_r_e_s_s
            contains the full address of the server to  which  this
            endpoint  will be connected.  This functions returns an
            opaque transport connection object on success, or  NULL
            on failure.

          +o XtransConnInfo TRANS(OpenCLTSServer)(char *address)

            This  function creates a Connection-Less Transport that
            is suitable for use by a server.  The parameter _a_d_d_r_e_s_s
            contains  the full address to which this server will be
            bound.  This  functions  returns  an  opaque  transport
            connection object on success, or NULL on failure.

          +o int   TRANS(SetOption)(XtransConnInfo  connection,  int
            option, int arg)

            This function sets transport options,  similar  to  the
            way  setsockopt()  and  ioctl()  work.   The  parameter
            _c_o_n_n_e_c_t_i_o_n  is  an  endpoint  that  was  obtained  from
            _XTransOpen*()   functions.    The   parameter   _o_p_t_i_o_n
            contains the option that will be set. The actual values
            for  _o_p_t_i_o_n  are  defined  in  a  later  section.   The
            parameter _a_r_g can be used  to  pass  in  an  additional
            value  that  may  be  required  by  some options.  This
            function return 0 on success and -1 on failure.

            Note:  Based  on  current  usage,   the   complimentary
            function TRANS(GetOption)() is not necessary.

          +o int   TRANS(CreateListener)(XtransConnInfo  connection,
            char *port)

            This  function  sets  up  the   server   endpoint   for
            listening.   The  parameter  _c_o_n_n_e_c_t_i_o_n  is an endpoint
            that  was  obtained  from  TRANS(OpenCOTSServer)()   or
            TRANS(OpenCLTSServer)().   The parameter _p_o_r_t specifies
            the port to which this endpoint  should  be  bound  for
            listening.   If  _p_o_r_t  is  NULL, then the transport may
            attempt  to  allocate  any  available  TSAP  for   this
            connection.  If the transport cannot support this, then
            this function will return  a  failure.   This  function












            return 0 on success and -1 on failure.

          +o int TRANS(ResetListener)(XtransConnInfo connection)

            When  a  server  is restarted, certain listen ports may
            need to be reset.  For example, unix  domain  needs  to
            check that the file used for communication has not been
            deleted.   If  it  has,  it  must  be  recreated.   The
            parameter  _c_o_n_n_e_c_t_i_o_n  is  an opened and bound endpoint
            that  was  obtained  from  TRANS(OpenCOTSServer)()  and
            passed  to TRANS(CreateListener)().  This function will
            return one of the following  values:  TRANS_RESET_NOOP,
            TRANS_RESET_NEW_FD, or TRANS_RESET_FAILURE.

          +o XtransConnInfo TRANS(Accept)(XtransConnInfo connection)

            Once a connection indication is received, this function
            can  be called to accept the connection.  The parameter
            _c_o_n_n_e_c_t_i_o_n is an opened and  bound  endpoint  that  was
            obtained  from  TRANS(OpenCOTSServer)()  and  passed to
            TRANS(CreateListener)().  This function will  return  a
            new  opaque  transport  connection object upon success,
            NULL otherwise.

          +o int  TRANS(Connect)(XtransConnInfo   connection,   char
            *address)

            This  function  creates  a connection to a server.  The
            parameter _c_o_n_n_e_c_t_i_o_n is an endpoint that  was  obtained
            from  TRANS(OpenCOTSClient)().   The parameters _a_d_d_r_e_s_s
            specify the TSAP to which this endpoint should connect.
            If  the protocol is included in the address, it will be
            ignored.  This function return 0 on success and  -1  on
            failure.

          +o int   TRANS(BytesReadable)(XtransConnInfo   connection,
            BytesReadable_t *pend);

            This function provides the same  functionality  as  the
            BytesReadable macro.

          +o int  TRANS(Read)(XtransConnInfo  connection, char *buf,
            int size)

            This function will return the number of bytes requested
            on  a  COTS  connection, and will return the minimum of
            the number bytes requested or the size of the  incoming
            packet on a CLTS connection.

          +o int  TRANS(Write)(XtransConnInfo connection, char *buf,
            int size)

            This function will write the requested number of  bytes
            on  a  COTS  connection,  and will send a packet of the












            requested size on a CLTS connection.

          +o int  TRANS(Readv)(XtransConnInfo   connection,   struct
            iovec *buf, int size)

            Similar to TRANS(Read)().

          +o int   TRANS(Writev)(XtransConnInfo  connection,  struct
            iovec *buf, int size)

            Similar to TRANS(Write)().

          +o int TRANS(Disconnect)(XtransConnInfo connection)

            This function is used when  an  orderly  disconnect  is
            desired.  This  function  breaks  the connection on the
            transport.  It  is  similar  to  the  socket   function
            shutdown().

          +o int TRANS(Close)(XtransConnInfo connection)

            This  function  closes  the  transport, unbinds it, and
            frees  all  resources  that  was  associated  with  the
            transport.  If a TRANS(Disconnect) call was not made on
            the connection, a disorderly disconnect may occur.

          +o int TRANS(IsLocal)(XtransConnInfo connection)

            Returns TRUE if it is a local transport.

          +o int TRANS(GetMyAddr)(XtransConnInfo connection,
                    int   *familyp,   int   *addrlenp,   Xtransaddr
            **addrp)

            This   function   is  similar  to  getsockname().  This
            function will allocate space for  the  address,  so  it
            must  be  freed by the caller.  Not all transports will
            have a valid address until a connection is established.
            This  function  should not be used until the connection
            is established with Connect() or Accept().

          +o int TRANS(GetPeerAddr)(XtransConnInfo connection,
                    int   *familyp,   int   *addrlenp,   Xtransaddr
            **addrp)

            This   function  is  similar  to  getpeername().   This
            function will allocate space for  the  address,  so  it
            must  be  freed by the caller.  Not all transports will
            have a valid address until a connection is established.
            This  function  should not be used until the connection
            is established with Connect() or Accept().

          +o int           TRANS(GetConnectionNumber)(XtransConnInfo
            connection)












            Returns   the  file  descriptor  associated  with  this
            transport.

          +o int TRANS(MakeAllCOTSServerListeners)(
                    char *port, int *partial_ret,  int  *count_ret,
            XtransConnInfo **connections_ret)

            This  function  should be used by most servers. It will
            try to  establish  a  COTS  server  endpoint  for  each
            transport  listed  in the transport table.  _p_a_r_t_i_a_l___r_e_t
            will be set to True if only a partial network could  be
            created.    _c_o_u_n_t___r_e_t   is  the  number  of  transports
            returns, and _c_o_n_n_e_c_t_i_o_n_s___r_e_t is the list of transports.

          +o int TRANS(MakeAllCLTSServerListeners)(
                    char  *port,  int *partial_ret, int *count_ret,
            XtransConnInfo **connections_ret)

            This function should be used by most servers.  It  will
            try  to  establish  a  CLTS  server  endpoint  for each
            transport listed in the transport  table.   _p_a_r_t_i_a_l___r_e_t
            will  be set to True if only a partial network could be
            created.   _c_o_u_n_t___r_e_t  is  the  number   of   transports
            returns, and _c_o_n_n_e_c_t_i_o_n_s___r_e_t is the list of transports.

       _5_._2  _U_t_i_l_i_t_y _A_P_I

       This section describes a few useful functions that have been
       implemented   on  top  of  the  Core  Interface  API.  These
       functions are being provided as a convenience.

          +o int TRANS(ConvertAddress)(int *familyp, int  *addrlenp,
            Xtransaddr *addrp)

            This function converts a sockaddr based address to an X
            authorization based address (ie AF_INET, AF_UNIX to the
            X     protocol     definition    (ie    FamilyInternet,
            FamilyLocal)).



       _6_.  _T_r_a_n_s_p_o_r_t _O_p_t_i_o_n _D_e_f_i_n_i_t_i_o_n

       The following options are defined for the TRANS(SetOption)()
       function.  If  an  OS  or  transport does not support any of
       these options, then it will silently ignore the option.

          +o TRANS_NONBLOCKING

            This  option  controls  the  blocking   mode   of   the
            connection.  If  the  argument  is  set  to 1, then the
            connection will be set to blocking. If the argument  is
            set  to  0,  then  the  connection  will be set to non-
            blocking.












          +o TRANS_CLOSEONEXEC

            This  option  determines  what  will  happen   to   the
            connection when an exec is encountered. If the argument
            is set to 1, then the connection will be closed when an
            exec  occurs.  If  the  argument  is set to 0, then the
            connection will not be closed when an exec occurs.


       _7_.  _H_i_d_d_e_n _T_r_a_n_s_p_o_r_t _D_e_p_e_n_d_e_n_t _A_P_I

       The hidden transport dependent functions are placed  in  the
       Xtransport  record.   These  function  are  similar  to  the
       Exposed  Transport  Independent  API,  but   some   of   the
       parameters  and return values are slightly different.  Stuff
       like the #ifdef  SUNSYSV  should  be  handled  inside  these
       functions.

          +o XtransConnInfo *OpenCOTSClient (
                    struct  _Xtransport *thistrans, char *protocol,
            char *host, char *port)

            This function creates a Connection-Oriented  Transport.
            The  parameter  _t_h_i_s_t_r_a_n_s points to an Xtransport entry
            in the transport table. The parameters _p_r_o_t_o_c_o_l,  _h_o_s_t,
            and  _p_o_r_t point to strings containing the corresponding
            parts   of   the   address   that   was   passed   into
            TRANS(OpenCOTSClient)().

            This function must allocate and initialize the contents
            of the XtransConnInfo structure  that  is  returned  by
            this  function.  This function will open the transport,
            and bind it into the transport namespace if applicable.
            The   local   address  portion  of  the  XtransConnInfo
            structure will also be filled in by this function.

          +o XtransConnInfo *OpenCOTSServer (
                    struct _Xtransport *thistrans, char  *protocol,
            char *host, char *port)

            This  function creates a Connection-Oriented Transport.
            The parameter _t_h_i_s_t_r_a_n_s points to an  Xtransport  entry
            in  the transport table. The parameters _p_r_o_t_o_c_o_l, _h_o_s_t,
            and _p_o_r_t point to strings containing the  corresponding
            parts   of   the   address   that   was   passed   into
            TRANS(OpenCOTSClient)().

            This function must allocate and initialize the contents
            of  the  XtransConnInfo  structure  that is returned by
            this function. This function will open the transport.

          +o XtransConnInfo *OpenCLTSClient (
                    struct _Xtransport *thistrans, char  *protocol,
            char *host, char *port)












            This  function creates a Connection-Less Transport. The
            parameter _t_h_i_s_t_r_a_n_s points to an  Xtransport  entry  in
            the transport table. The parameters _p_r_o_t_o_c_o_l, _h_o_s_t, and
            _p_o_r_t point  to  strings  containing  the  corresponding
            parts   of   the   address   that   was   passed   into
            TRANS(OpenCOTSClient)().

            This function must allocate and initialize the contents
            of  the  XtransConnInfo  structure  that is returned by
            this function. This function will open  the  transport,
            and bind it into the transport namespace if applicable.
            The  local  address  portion  of   the   XtransConnInfo
            structure will also be filled in by this function.

          +o XtransConnInfo *OpenCLTSServer (
                    struct  _Xtransport *thistrans, char *protocol,
            char *host, char *port)

            This function creates a Connection-Less Transport.  The
            parameter  _t_h_i_s_t_r_a_n_s  points  to an Xtransport entry in
            the transport table. The parameters _p_r_o_t_o_c_o_l, _h_o_s_t, and
            _p_o_r_t  point  to  strings  containing  the corresponding
            parts   of   the   address   that   was   passed   into
            TRANS(OpenCOTSClient)().

            This function must allocate and initialize the contents
            of the XtransConnInfo structure  that  is  returned  by
            this function. This function will open the transport.

          +o int   SetOption  (struct  _Xtransport  *thistrans,  int
            option, int arg)

            This function provides a  transport  dependent  way  of
            implementing  the  options  defined  by the X Transport
            Interface. In the current prototype, this  function  is
            not  being  used,  because all of the option defined so
            far, are transport independent. This function will have
            to  be  used if a radically different transport type is
            added, or a transport dependent option is defined.

          +o int CreateListener (struct _Xtransport *thistrans, char
            *port )

            This  function  takes a transport endpoint opened for a
            server,  and  sets  it  up  to  listen   for   incoming
            connection  requests. The parameter _p_o_r_t should contain
            the port portion of the address that was passed to  the
            Open function.

            This   function   will  bind  the  transport  into  the
            transport name space if applicable,  and  fill  in  the
            local  address portion of the XtransConnInfo structure.
            The transport endpoint will then be set to  listen  for
            incoming connection requests.












          +o int ResetListener (struct _Xtransport *thistrans)

            This function resets the transport for listening.

          +o XtransConnInfo Accept(struct _Xtransport *thistrans)

            This  function  creates  a  new transport endpoint as a
            result of an incoming connection request. The parameter
            _t_h_i_s_t_r_a_n_s is the endpoint that was opened for listening
            by the server. The new endpoint  is  opened  and  bound
            into   the   transport's  namespace.  A  XtransConnInfo
            structure describing the new endpoint is returned  from
            this function

          +o int  Connect(struct _Xtransport *thistrans, char *host,
            char *port )

            This function establishes a connection to a server. The
            parameters  _h_o_s_t  and _p_o_r_t describe the server to which
            the connection should be  established.  The  connection
            will be established so that Read() and Write() call can
            be made.

          +o int   BytesReadable(struct   _Xtransport    *thistrans,
            BytesReadable_t *pend )

            This  function replaces the BytesReadable() macro. This
            allows each transport to have it's  own  mechanism  for
            determining how much data is ready to be read.

          +o int  Read(struct _Xtransport *thistrans, char *buf, int
            size )

            This function  reads  _s_i_z_e  bytes  into  _b_u_f  from  the
            connection.

          +o int Write(struct _Xtransport *thistrans, char *buf, int
            size )

            This  function  writes  _s_i_z_e  bytes  from  _b_u_f  to  the
            connection.

          +o int  Readv(struct  _Xtransport *thistrans, struct iovec
            *buf, int size )

            This function performs a readv() on the connection.

          +o int Writev(struct _Xtransport *thistrans, struct  iovec
            *buf, int size )

            This function performs a writev() on the connection.

          +o int Disconnect(struct _Xtransport *thistrans)













            This  function  initiates  an  orderly  shutdown  of  a
            connection. If a transport does not distinguish between
            orderly and disorderly disconnects, then a call to this
            function will have no affect.

          +o int Close(struct _Xtransport *thistrans)

            This function will break the connection, and close  the
            endpoint.


       _8_.  _C_o_n_f_i_g_u_r_a_t_i_o_n

       The   implementation  of  each  transport  can  be  platform
       specific. It is expected that existing connection types such
       as  TCPCONN,  UNIXCONN,  LOCALCONN  and  STREAMSCONN will be
       replaced with flags for each possible transport type.

       Below are the flags that can be set  in  _C_o_n_n_e_c_t_i_o_n_F_l_a_g_s  in
       the vendor.cf or site.def config files.

       TCPCONN       Enables the INET Domain Socket based transport
       UNIXCONN      Enables the UNIX Domain Sokcet based transport
       STREAMSCONN   Enables the TLI based transports
       LOCALCONN     Enables the SYSV Local connection transports
       DNETCONN      Enables the DECnet transports


       _9_.  _T_r_a_n_s_p_o_r_t _S_p_e_c_i_f_i_c _D_e_f_i_n_i_t_i_o_n_s





































       +---------+------------------------------------------------------------------+
       |PPrroottooccooll |                        AAddddrreessss CCoommppoonneenntt                         |
       |         +----------+--------------------------------------+----------------+
       |FFaammiillyy   | pprroottooccooll |                 hhoosstt                 |      ppoorrtt      |
       +---------+----------+--------------------------------------+----------------+
       |Internet | inet     | name of an internet addressable host | string         |
       |         | tcp      |                                      | containing     |
       |         | udp      |                                      | the  name of   |
       |         |          |                                      | a service or   |
       |         |          |                                      | a valid port   |
       |         |          |                                      | number.        |
       |         |          |                                      | Example:       |
       |         |          |                                      | "xserver0",    |
       |         |          |                                      | "7100"         |
       +---------+----------+--------------------------------------+----------------+
       |DECnet   | decnet   | name of a DECnet addressable host    | string         |
       |         |          |                                      | containing     |
       |         |          |                                      | the complete   |
       |         |          |                                      | name  of the   |
       |         |          |                                      | object.        |
       |         |          |                                      | Example:       |
       |         |          |                                      | "X$X0"         |
       +---------+----------+--------------------------------------+----------------+
       |NETware  | ipx      | name of a NETware addressable host   | Not  sure of   |
       |         |          |                                      | the            |
       |         |          |                                      | specifics      |
       |         |          |                                      | yet.           |
       +---------+----------+--------------------------------------+----------------+
       |OSI      | osi      | name of an OSI addressable host      | Not sure  of   |
       |         |          |                                      | the            |
       |         |          |                                      | specifics      |
       |         |          |                                      | yet.           |
       +---------+----------+--------------------------------------+----------------+
       |Local    | local    | (ignored)                            | String         |
       |         | pts      |                                      | containing     |
       |         | named    |                                      | the     port   |
       |         | sco      |                                      | name,     ie   |
       |         | isc      |                                      | "xserver0",    |
       |         |          |                                      | "fontserver0". |
       +---------+----------+--------------------------------------+----------------+

       _1_0_.  _I_m_p_l_e_m_e_n_t_a_t_i_o_n _N_o_t_e_s

       This  section refers to the prototype implementation that is
       being  developed  concurrently  with  this  document.   This
       prototype  has  been  able  to  flush  out  many details and
       problems as the specification was being developed.

       All of the source code for  this  interface  is  located  in
       xc/lib/xtrans.

       All  functions  names  in  the  source  are  of  the  format
       TRANS(func)(). The TRANS() macro is defined as













       #if (__STDC__ && !defined(UNIXCPP)) || defined(ANSICPP)
       #define TRANS(func) _PROTOCOLTrans##func
       #else
       #define TRANS(func) _PROTOCOLTrans/**/func
       #endif


       PROTOCOL will be uniquely defined in  each  directory  where
       this  code  is  compiled. PROTOCOL will be defined to be the
       name of the protocol that is implemented by the  library  or
       server, such as X11, FS, and ICE.

       All libraries and servers that use the X Transport Interface
       should have a new file called transport.c.  This  file  will
       include  the  transports  based  on  the configuration flags
       _C_o_n_n_e_c_t_i_o_n_F_l_a_g_s. Below is an example transport.c.

       #include "Xtransint.h"

       #ifdef DNETCONN
       #include "Xtransdnet.c"
       #endif
       #ifdef LOCALCONN
       #include "Xtranslocal.c"
       #endif
       #ifdef TCPCONN
       #include "Xtranssock.c"
       #endif
       #ifdef STREAMSCONN
       #include "Xtranstli.c"
       #endif
       #include "Xtrans.c"
       #include "Xtransutil.c"


       The source files for this interface are listed below.

       Xtrans.h        Function prototypes and defines for
                       the Transport Independent API.
       Xtransint.h     Used by the interface implementation only.
                       Contains the internal data structures.
       Xtranssock.c    Socket implementation of the Transport Dependent API.
       Xtranstli.c     TLI implementation of the Transport Dependent API.
       Xtransdnet.c    DECnet implementation of the Transport Dependent API.
       Xtranslocal.c   Implementation of the Transport Dependent API for
                       SYSV Local connections.
       Xtrans.c        Exposed Transport Independent API Functions.
       Xtransutil.c    Collection of Utility functions that use the
                       X Transport Interface.


       The file _X_t_r_a_n_s_i_n_t_._h contains much of the transport  related
       code  that  previously in Xlibint.h and Xlibnet.h. This will
       make the definitions available for all transport users. This












       should also obsolete the equivilent code in other libraries.


























































