path: root/lib/ssh/doc/src/ssh_connection.xml

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<!DOCTYPE erlref SYSTEM "erlref.dtd">

<erlref>
  <header>
    <copyright>
      <year>2008</year>
      <year>2012</year>
      <holder>Ericsson AB, All Rights Reserved</holder>
    </copyright>
    <legalnotice>
  The contents of this file are subject to the Erlang Public License,
  Version 1.1, (the "License"); you may not use this file except in
  compliance with the License. You should have received a copy of the
  Erlang Public License along with this software. If not, it can be
  retrieved online at http://www.erlang.org/.

  Software distributed under the License is distributed on an "AS IS"
  basis, WITHOUT WARRANTY OF ANY KIND, either express or implied. See
  the License for the specific language governing rights and limitations
  under the License.

  The Initial Developer of the Original Code is Ericsson AB.
    </legalnotice>

    <title>ssh_connection</title>
    <date></date>
  </header>
  <module>ssh_connection</module>
  <modulesummary>This module provides API functions to send <url href="http://www.ietf.org/rfc/rfc4254.txt"> SSH Connection Protocol </url>
  events to the other side of an SSH channel.
  </modulesummary>

  <description>
    <p>The SSH Connection Protocol is used by clients and servers
    (i.e. SSH channels) to communicate over the SSH connection. The
    API functions in this module sends SSH Connection Protocol events
    that are received as messages by the remote channel.
    In the case that the receiving channel is an Erlang process the
    message will be on the following format
    <c><![CDATA[{ssh_cm, ssh_connection_ref(), ssh_event_msg()}]]></c>. If the <seealso
    marker="ssh_channel">ssh_channel</seealso> behavior is used to
    implement the channel process these will be handled by
    <seealso
	marker="ssh_channel#CallbackModule:handled_ssh_msg-2">handle_ssh_msg/2 </seealso>.</p>
  </description>

  <section>
    <title>DATA TYPES </title>

    <p>Type definitions that are used more than once in this module and/or
    abstractions to indicate the intended use of the data type:</p>

    <p><c>boolean() = true | false </c></p>
    <p><c>string() = list of ASCII characters</c></p>
    <p><c>timeout() =  infinity | integer() - in milliseconds.</c></p>
    <p><c>ssh_connection_ref() - opaque to the user returned by
    ssh:connect/3 or sent to an SSH channel processes</c></p>
    <p><c>ssh_channel_id() = integer() </c></p>
    <p><c>ssh_data_type_code() = 1 ("stderr") | 0 ("normal") are
    currently valid values see</c> <url href="http://www.ietf.org/rfc/rfc4254.txt">RFC 4254  </url> section 5.2.</p>
    <p><c>ssh_request_status() = success | failure</c></p>
    <p><c>event() = {ssh_cm, ssh_connection_ref(), ssh_event_msg()} </c></p>
    <p><c>ssh_event_msg()  = data_events() | status_events() | terminal_events() </c></p>

    <taglist>
      <tag><b>data_events()</b></tag>
       <item>
	 <taglist>
	   <tag><c><![CDATA[{data, ssh_channel_id(), ssh_data_type_code(), binary() = Data}]]></c></tag>
	   <item> Data has arrived on the channel. This event is sent as
	   result of calling <seealso marker="#send-3"> ssh_connection:send/[3,4,5] </seealso></item>

	   <tag><c><![CDATA[{eof, ssh_channel_id()}]]></c></tag>
	   <item>Indicates that the other side will not send any more
	   data. This event is sent as result of calling <seealso
	   marker="#send_eof-2"> ssh_connection:send_eof/2</seealso>
	   </item>
	 </taglist>
       </item>

       <tag><b>status_events()</b></tag>
       <item>

      <taglist>
	<tag><c><![CDATA[{signal, ssh_channel_id(), ssh_signal()}]]></c></tag>
	<item>A signal can be delivered to the remote process/service
	using the following message. Some systems will not support
	signals, in which case they should ignore this message. There is
	currently no funtion to generate this event as the signals
	refered to are on OS-level and not something generated by an
	Erlang program.</item>

	<tag><c><![CDATA[{exit_signal, ssh_channel_id(), string() = exit_signal, string() = ErrorMsg,
	string() = LanguageString}]]></c></tag>

	<item>A remote execution may terminate violently due to a signal
	then this message may be received. For details on valid string
	values see  <url href="http://www.ietf.org/rfc/rfc4254.txt">RFC 4254</url> section 6.10. Special case of the signals
	mentioned above.</item>

	<tag><c><![CDATA[{exit_status, ssh_channel_id(), integer() = ExitStatus}]]></c></tag>
	<item> When the command running at the other end terminates, the
	following message can be sent to return the exit status of the
	command. A zero 'exit_status' usually means that the command
	terminated successfully. This event is sent as result of calling
	<seealso marker="#exit_status">
	ssh_connection:exit_status/3</seealso></item>

	<tag><c><![CDATA[{closed, ssh_channel_id()}]]></c></tag>
	<item> This event is sent as result of calling
	<seealso marker="#close">ssh_connection:close/2</seealso> Both the handling of this
	event and sending of it will be taken care of by the
	<seealso marker="ssh_channel">ssh_channel</seealso> behavior.</item>

      </taglist>
     </item>

     <tag><b>terminal_events()</b></tag>

     <item>
       <p> Channels implementing a shell and command execution on the
       server side should handle the following messages that may be sent by client channel processes. </p>

       <p><note>Events that includes a  <c> WantReply</c> expects the event handling
       process to call <seealso marker="#reply_request">ssh_connection:reply_request/4</seealso>
       with the boolean value of <c> WantReply</c> as the second
       argument. </note> </p>

       <taglist>
	 <tag><c><![CDATA[{env, ssh_channel_id(), boolean() = WantReply,
	 string() = Var, string() = Value}]]></c></tag>
	 <item> Environment variables may be passed to the shell/command
	 to be started later. This event is sent as result of calling <seealso
	 marker="#setenv"> ssh_connection:setenv/5</seealso>
	 </item>

	 <tag><c><![CDATA[{pty, ssh_channel_id(),
	 boolean() = WantReply, {string() = Terminal, integer() = CharWidth,
	 integer() = RowHeight, integer() = PixelWidth, integer() = PixelHight,
	 [{atom() | integer() = Opcode,
	 integer() = Value}] = TerminalModes}}]]></c></tag>
	 <item>A pseudo-terminal has been requested for the
	 session. Terminal is the value of the TERM environment
	 variable value (e.g., vt100). Zero dimension parameters must
	 be ignored.  The character/row dimensions override the pixel
	 dimensions (when nonzero).  Pixel dimensions refer to the
	 drawable area of the window. The <c>Opcode</c> in the
	 <c>TerminalModes</c> list is the mnemonic name, represented
	 as an lowercase erlang atom, defined in
	 <url href="http://www.ietf.org/rfc/rfc4254.txt">RFC 4254  </url> section 8,
	 or the opcode if the mnemonic name is not listed in the
	 RFC. Example <c>OP code: 53, mnemonic name ECHO erlang atom:
	 echo</c>. There is currently no API function to generate this
	 event.</item>

	 <tag><c><![CDATA[{shell, boolean() = WantReply}]]></c></tag>
	 <item> This message will request that the user's default shell
	 be started at the other end. This event is sent as result of calling <seealso
	 marker="#shell"> ssh_connection:shell/2</seealso>
	 </item>

	 <tag><c><![CDATA[{window_change, ssh_channel_id(), integer() = CharWidth,
	 integer() = RowHeight, integer() = PixWidth, integer() = PixHeight}]]></c></tag>
	 <item> When the window (terminal) size changes on the client
	 side, it MAY send a message to the server side to inform it of
	 the new dimensions. There is currently no API function to generate this
	 event.</item>
     
	 <tag><c><![CDATA[{exec, ssh_channel_id(),
	 boolean() = WantReply, string() = Cmd}]]></c></tag>
	 <item> This message will request that the server starts
	 execution of the given command. This event is sent as result of calling <seealso
	 marker="#exec">ssh_connection:exec/4 </seealso>
	 </item>
       </taglist>
     </item>
   </taglist>
 </section>

  <funcs>
   
   <func>
     <name>adjust_window(ConnectionRef, ChannelId, NumOfBytes) -> ok</name>
     <fsummary>Adjusts the SSH flowcontrol window. </fsummary>
     <type>
       <v> ConnectionRef = ssh_connection_ref() </v>
       <v> ChannelId = ssh_channel_id() </v>
       <v> NumOfBytes = integer()</v>
     </type>
      <desc>
	<p>Adjusts the SSH flowcontrol window. This shall be done by both client and server side channel processes.</p>
	
	<note><p>Channels implemented with the <seealso marker="ssh_channel"> ssh_channel
	behavior</seealso> will normaly not need to call this function as flow control
	will be handled by the behavior. The behavior will adjust the window every time
	the callback <seealso marker="ssh_channel#handled_ssh_msg-2">
	handle_ssh_msg/2 </seealso> has returned after processing channel data</p> </note>
      </desc>
   </func>
   
   <func>
     <name>close(ConnectionRef, ChannelId) -> ok</name>
     <fsummary>Sends a close message on the channel <c>ChannelId</c>. </fsummary>
     <type>
       <v> ConnectionRef = ssh_connection_ref() </v>
       <v> ChannelId = ssh_channel_id()</v>
     </type>
     <desc>
       <p>A server or client channel process can choose to close their session by sending a close event.
       </p>

       <note><p>This function will be called by the ssh_channel
       behavior when the channel is terminated see <seealso
       marker="ssh_channel"> ssh_channel(3) </seealso> so channels implemented with the
       behavior should not call this function explicitly.</p></note>
     </desc>
   </func>
   
   <func>
     <name>exec(ConnectionRef, ChannelId, Command, TimeOut) -> ssh_request_status()  </name>
     <fsummary>Request that the server start the execution of the given command.  </fsummary>
     <type>
       <v> ConnectionRef = ssh_connection_ref() </v>
       <v> ChannelId = ssh_channel_id()</v>
       <v> Command = string()</v>
       <v>Timeout = timeout() </v>
     </type>
     <desc>
       <p>Should be called by a client channel process to request that the server starts execution of the
       given command, the result will be several messages according to the following pattern. Note
       that the last message will be a channel close message, as the exec request is a one time
       execution that closes the channel when it is done.</p>

       <taglist>
	 <tag><c> N x {ssh_cm, ssh_connection_ref(),
	 {data, ssh_channel_id(), ssh_data_type_code(), binary() = Data}} </c></tag>
	 <item>The result of executing the command may be only one line
	 or thousands of lines depending on the command.</item>

	 <tag><c>0 or 1 x {ssh_cm, ssh_connection_ref(), {eof, ssh_channel_id()}}</c></tag>
	 <item>Indicates that no more data will be sent.</item>

	 <tag><c>0 or 1 x {ssh_cm,
	 ssh_connection_ref(), {exit_signal,
	 ssh_channel_id(), string() = ExitSignal, string() = ErrorMsg, string() = LanguageString}}</c></tag>
	 <item>Not all systems send signals. For details on valid string
	 values see RFC 4254 section 6.10 </item>
	 
	  <tag><c>0 or 1 x {ssh_cm, ssh_connection_ref(), {exit_status,
	  ssh_channel_id(), integer() = ExitStatus}}</c></tag>
	  <item>It is recommended by the <c>ssh connection protocol</c> that this
	  message shall be sent, but that may not always be the case.</item>

	  <tag><c> 1 x {ssh_cm, ssh_connection_ref(),
	  {closed, ssh_channel_id()}}</c></tag>
	  <item>Indicates that the ssh channel started for the
	  execution of the command has now been shutdown.</item>
       </taglist>
     </desc>
   </func>

   <func>
     <name>exit_status(ConnectionRef, ChannelId, Status) -> ok</name>
     <fsummary>Sends the exit status of a command to the client.</fsummary>
     <type>
       <v> ConnectionRef = ssh_connection_ref() </v>
       <v> ChannelId = ssh_channel_id()</v>
       <v> Status = integer()</v>
     </type>
     <desc>
       <p>Should be called by a server channel process to sends the exit status of a command to the client.</p>
     </desc>
   </func>
   
     <func>
       <name>reply_request(ConnectionRef, WantReply, Status, CannelId) -> ok</name>
       <fsummary>Send status replies to requests that want such replies. </fsummary>
      <type>
	<v> ConnectionRef = ssh_connection_ref() </v>
	<v> WantReply =  boolean()</v>
	<v> Status = ssh_request_status() </v>
	<v> ChannelId = ssh_channel_id()</v>
      </type>
      <desc>
	<p>Sends status replies to requests where the requester has
	stated that they want a status report e.i .<c> WantReply = true</c>,
	if <c> WantReply</c> is false calling this function will be a
	"noop". Should be called while handling an ssh connection
	protocol message containing a <c>WantReply</c> boolean
	value.
	</p>
      </desc>
     </func>
    
     <func>
       <name>send(ConnectionRef, ChannelId, Data) -></name>
       <name>send(ConnectionRef, ChannelId, Data, Timeout) -></name>
       <name>send(ConnectionRef, ChannelId, Type, Data) -></name>
       <name>send(ConnectionRef, ChannelId, Type, Data, TimeOut) ->
       ok | {error, timeout} | {error, closed}</name>
       <fsummary>Sends channel data </fsummary>
       <type>
	<v> ConnectionRef = ssh_connection_ref() </v>
	<v> ChannelId = ssh_channel_id()</v>
	<v> Data = binary()</v>
	<v> Type = ssh_data_type_code()</v>
	<v> Timeout = timeout()</v>
       </type>
       <desc>
	 <p>Should be called by client- and server channel processes to send data to each other.
	 </p>
       </desc>
     </func>
     
     <func>
       <name>send_eof(ConnectionRef, ChannelId) -> ok | {error, closed}</name>
       <fsummary>Sends eof on the channel <c>ChannelId</c>.  </fsummary>
       <type>
	<v> ConnectionRef = ssh_connection_ref() </v>
	<v> ChannelId = ssh_channel_id()</v>
       </type>
       <desc>
	 <p>Sends eof on the channel <c>ChannelId</c>.
	 </p>
       </desc>
     </func>

     <func>
       <name>session_channel(ConnectionRef, Timeout) -> </name>
       <name>session_channel(ConnectionRef, InitialWindowSize,
       MaxPacketSize, Timeout) -> {ok, ssh_channel_id()} | {error, Reason}</name>
       <fsummary>Opens a channel for a ssh session. </fsummary>
       <type>
	 <v> ConnectionRef = ssh_connection_ref()</v>
	 <v> InitialWindowSize = integer() </v>
	 <v> MaxPacketSize = integer() </v>
	 <v> Timeout = timeout()</v>
	 <v> Reason = term() </v>
       </type>
       <desc>
	 <p>Opens a channel for an SSH session. The channel id returned from this function
	 is the id used as input to the other funtions in this module.
	</p>
       </desc>
     </func>

    <func>
      <name>setenv(ConnectionRef, ChannelId, Var, Value, TimeOut) -> ssh_request_status()</name>
      <fsummary> Environment variables may be passed to the
      shell/command to be started later.</fsummary>
      <type>
	<v> ConnectionRef = ssh_connection_ref() </v>
	<v> ChannelId = ssh_channel_id()</v>
	<v> Var = string()</v>
	<v> Value = string()</v>
	<v> Timeout = timeout()</v>
      </type>
      <desc>
	<p> Environment variables may be passed before starting the
	shell/command. Should be called by a client channel processes.
	</p>
      </desc>
    </func>
    
    <func>
      <name>shell(ConnectionRef, ChannelId) -> ssh_request_status()
      </name>
      <fsummary> Requests that the user's default shell (typically
      defined in /etc/passwd in UNIX systems) shall be executed at the server
      end. </fsummary>
       <type>
	 <v> ConnectionRef = ssh_connection_ref() </v>
	 <v> ChannelId = ssh_channel_id()</v>
       </type>
       <desc>
	 <p> Should be called by a client channel process to request that the user's default shell (typically
	 defined in /etc/passwd in UNIX systems) shall be executed at the server end.
	 </p>
       </desc>
    </func>

    <func>
      <name>subsystem(ConnectionRef, ChannelId, Subsystem, Timeout) -> ssh_request_status()</name>
      <fsummary>  </fsummary>
       <type>
	 <v> ConnectionRef = ssh_connection_ref() </v>
	 <v> ChannelId = ssh_channel_id()</v>
	 <v> Subsystem = string()</v>
	 <v> Timeout = timeout()</v>
       </type>
       <desc>
	 <p> Should be called by a client channel process for requesting to execute a predefined subsystem on the server.
	 </p>
       </desc>
    </func>
    
  </funcs>
  
</erlref>