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Net::SSH::Connection::Session

A session class representing the connection service running on top of the SSH transport layer. It manages the creation of channels (see #), and the dispatching of messages to the various channels. It also encapsulates the SSH event loop (via # and #), and serves as a central point-of-reference for all SSH-related services (e.g. port forwarding, SFTP, SCP, etc.).

You will rarely (if ever) need to instantiate this class directly; rather, you’ll almost always use Net::SSH.start to initialize a new network connection, authenticate a user, and return a new connection session, all in one call.

  Net::SSH.start("localhost", "user") do |ssh|
    # 'ssh' is an instance of Net::SSH::Connection::Session
    ssh.exec! "/etc/init.d/some_process start"
  end

Constants

MAP

Attributes

transport[R]

The underlying transport layer abstraction (see Net::SSH::Transport::Session).

options[R]

The map of options that were used to initialize this instance.

properties[R]

The collection of custom properties for this instance. (See #[] and #[]=).

Public Class Methods

new(transport, options={}) click to toggle source

Create a new connection service instance atop the given transport layer. Initializes the listeners to be only the underlying socket object.

    # File lib/net/ssh/connection/session.rb, line 62
62:     def initialize(transport, options={})
63:       self.logger = transport.logger
64: 
65:       @transport = transport
66:       @options = options
67: 
68:       @channel_id_counter = 1
69:       @channels = Hash.new(NilChannel.new(self))
70:       @listeners = { transport.socket => nil }
71:       @pending_requests = []
72:       @channel_open_handlers = {}
73:       @on_global_request = {}
74:       @properties = (options[:properties] || {}).dup
75:     end

Public Instance Methods

[](key) click to toggle source

Retrieves a custom property from this instance. This can be used to store additional state in applications that must manage multiple SSH connections.

    # File lib/net/ssh/connection/session.rb, line 80
80:     def [](key)
81:       @properties[key]
82:     end
[]=(key, value) click to toggle source

Sets a custom property for this instance.

    # File lib/net/ssh/connection/session.rb, line 85
85:     def []=(key, value)
86:       @properties[key] = value
87:     end
busy?(include_invisible=false) click to toggle source

Returns true if there are any channels currently active on this session. By default, this will not include “invisible” channels (such as those created by forwarding ports and such), but if you pass a true value for include_invisible, then those will be counted.

This can be useful for determining whether the event loop should continue to be run.

  ssh.loop { ssh.busy? }
     # File lib/net/ssh/connection/session.rb, line 134
134:     def busy?(include_invisible=false)
135:       if include_invisible
136:         channels.any?
137:       else
138:         channels.any? { |id, ch| !ch[:invisible] }
139:       end
140:     end
close() click to toggle source

Closes the session gracefully, blocking until all channels have successfully closed, and then closes the underlying transport layer connection.

     # File lib/net/ssh/connection/session.rb, line 107
107:     def close
108:       info { "closing remaining channels (#{channels.length} open)" }
109:       channels.each { |id, channel| channel.close }
110:       loop { channels.any? }
111:       transport.close
112:     end
closed?() click to toggle source

Returns true if the underlying transport has been closed. Note that this can be a little misleading, since if the remote server has closed the connection, the local end will still think it is open until the next operation on the socket. Nevertheless, this method can be useful if you just want to know if you have closed the connection.

     # File lib/net/ssh/connection/session.rb, line 100
100:     def closed?
101:       transport.closed?
102:     end
exec(command, &block) click to toggle source

A convenience method for executing a command and interacting with it. If no block is given, all output is printed via $stdout and $stderr. Otherwise, the block is called for each data and extended data packet, with three arguments: the channel object, a symbol indicating the data type (:stdout or :stderr), and the data (as a string).

Note that this method returns immediately, and requires an event loop (see Session#loop) in order for the command to actually execute.

This is effectively identical to calling #, and then Net::SSH::Connection::Channel#exec, and then setting up the channel callbacks. However, for most uses, this will be sufficient.

  ssh.exec "grep something /some/files" do |ch, stream, data|
    if stream == :stderr
      puts "ERROR: #{data}"
    else
      puts data
    end
  end
     # File lib/net/ssh/connection/session.rb, line 319
319:     def exec(command, &block)
320:       open_channel do |channel|
321:         channel.exec(command) do |ch, success|
322:           raise "could not execute command: #{command.inspect}" unless success
323:           
324:           channel.on_data do |ch2, data|
325:             if block
326:               block.call(ch2, :stdout, data)
327:             else
328:               $stdout.print(data)
329:             end
330:           end
331: 
332:           channel.on_extended_data do |ch2, type, data|
333:             if block
334:               block.call(ch2, :stderr, data)
335:             else
336:               $stderr.print(data)
337:             end
338:           end
339:         end
340:       end
341:     end
exec!(command, &block) click to toggle source

Same as #, except this will block until the command finishes. Also, if a block is not given, this will return all output (stdout and stderr) as a single string.

  matches = ssh.exec!("grep something /some/files")
     # File lib/net/ssh/connection/session.rb, line 348
348:     def exec!(command, &block)
349:       block ||= Proc.new do |ch, type, data|
350:         ch[:result] ||= ""
351:         ch[:result] << data
352:       end
353: 
354:       channel = exec(command, &block)
355:       channel.wait
356: 
357:       return channel[:result]
358:     end
forward() click to toggle source

Returns a reference to the Net::SSH::Service::Forward service, which can be used for forwarding ports over SSH.

     # File lib/net/ssh/connection/session.rb, line 417
417:     def forward
418:       @forward ||= Service::Forward.new(self)
419:     end
host() click to toggle source

Returns the name of the host that was given to the transport layer to connect to.

    # File lib/net/ssh/connection/session.rb, line 91
91:     def host
92:       transport.host
93:     end
listen_to(io, &callback) click to toggle source

Adds an IO object for the event loop to listen to. If a callback is given, it will be invoked when the io is ready to be read, otherwise, the io will merely have its # method invoked.

Any io value passed to this method must have mixed into it the Net::SSH::BufferedIo functionality, typically by calling # on the object.

The following example executes a process on the remote server, opens a socket to somewhere, and then pipes data from that socket to the remote process’ stdin stream:

  channel = ssh.open_channel do |ch|
    ch.exec "/some/process/that/wants/input" do |ch, success|
      abort "can't execute!" unless success

      io = TCPSocket.new(somewhere, port)
      io.extend(Net::SSH::BufferedIo)
      ssh.listen_to(io)

      ch.on_process do
        if io.available > 0
          ch.send_data(io.read_available)
        end
      end

      ch.on_close do
        ssh.stop_listening_to(io)
        io.close
      end
    end
  end

  channel.wait
     # File lib/net/ssh/connection/session.rb, line 405
405:     def listen_to(io, &callback)
406:       listeners[io] = callback
407:     end
loop(wait=nil, &block) click to toggle source

The main event loop. Calls # until # returns false. If a block is given, it is passed to #, otherwise a default proc is used that just returns true if there are any channels active (see #). The # wait parameter is also passed through to # (where it is interpreted as the maximum number of seconds to wait for IO.select to return).

  # loop for as long as there are any channels active
  ssh.loop

  # loop for as long as there are any channels active, but make sure
  # the event loop runs at least once per 0.1 second
  ssh.loop(0.1)

  # loop until ctrl-C is pressed
  int_pressed = false
  trap("INT") { int_pressed = true }
  ssh.loop(0.1) { not int_pressed }
     # File lib/net/ssh/connection/session.rb, line 159
159:     def loop(wait=nil, &block)
160:       running = block || Proc.new { busy? }
161:       loop_forever { break unless process(wait, &running) }
162:     end
Also aliased as: loop_forever
loop_forever(wait=nil, &block) click to toggle source

preserve a reference to Kernel#loop

Alias for: loop
on_global_request(type, &block) click to toggle source

Registers a handler to be invoked when the server sends a global request of the given type. The callback receives the request data as the first parameter, and true/false as the second (indicating whether a response is required). If the callback sends the response, it should return :sent. Otherwise, if it returns true, REQUEST_SUCCESS will be sent, and if it returns false, REQUEST_FAILURE will be sent.

     # File lib/net/ssh/connection/session.rb, line 441
441:     def on_global_request(type, &block)
442:       old, @on_global_request[type] = @on_global_request[type], block
443:       old
444:     end
on_open_channel(type, &block) click to toggle source

Registers a handler to be invoked when the server wants to open a channel on the client. The callback receives the connection object, the new channel object, and the packet itself as arguments, and should raise ChannelOpenFailed if it is unable to open the channel for some reason. Otherwise, the channel will be opened and a confirmation message sent to the server.

This is used by the Net::SSH::Service::Forward service to open a channel when a remote forwarded port receives a connection. However, you are welcome to register handlers for other channel types, as needed.

     # File lib/net/ssh/connection/session.rb, line 431
431:     def on_open_channel(type, &block)
432:       channel_open_handlers[type] = block
433:     end
open_channel(type="session", *extra, &on_confirm) click to toggle source

Requests that a new channel be opened. By default, the channel will be of type “session”, but if you know what you’re doing you can select any of the channel types supported by the SSH protocol. The extra parameters must be even in number and conform to the same format as described for Net::SSH::Buffer.from. If a callback is given, it will be invoked when the server confirms that the channel opened successfully. The sole parameter for the callback is the channel object itself.

In general, you’ll use # without any arguments; the only time you’d want to set the channel type or pass additional initialization data is if you were implementing an SSH extension.

  channel = ssh.open_channel do |ch|
    ch.exec "grep something /some/files" do |ch, success|
      ...
    end
  end

  channel.wait
     # File lib/net/ssh/connection/session.rb, line 287
287:     def open_channel(type="session", *extra, &on_confirm)
288:       local_id = get_next_channel_id
289:       channel = Channel.new(self, type, local_id, &on_confirm)
290: 
291:       msg = Buffer.from(:byte, CHANNEL_OPEN, :string, type, :long, local_id,
292:         :long, channel.local_maximum_window_size,
293:         :long, channel.local_maximum_packet_size, *extra)
294:       send_message(msg)
295: 
296:       channels[local_id] = channel
297:     end
postprocess(readers, writers) click to toggle source

This is called internally as part of #. It loops over the given arrays of reader IO’s and writer IO’s, processing them as needed, and then calls Net::SSH::Transport::Session#rekey_as_needed to allow the transport layer to rekey. Then returns true.

     # File lib/net/ssh/connection/session.rb, line 223
223:     def postprocess(readers, writers)
224:       Array(readers).each do |reader|
225:         if listeners[reader]
226:           listeners[reader].call(reader)
227:         else
228:           if reader.fill.zero?
229:             reader.close
230:             stop_listening_to(reader)
231:           end
232:         end
233:       end
234: 
235:       Array(writers).each do |writer|
236:         writer.send_pending
237:       end
238: 
239:       transport.rekey_as_needed
240: 
241:       return true
242:     end
preprocess() click to toggle source

This is called internally as part of #. It dispatches any available incoming packets, and then runs Net::SSH::Connection::Channel#process for any active channels. If a block is given, it is invoked at the start of the method and again at the end, and if the block ever returns false, this method returns false. Otherwise, it returns true.

     # File lib/net/ssh/connection/session.rb, line 211
211:     def preprocess
212:       return false if block_given? && !yield(self)
213:       dispatch_incoming_packets
214:       channels.each { |id, channel| channel.process unless channel.closing? }
215:       return false if block_given? && !yield(self)
216:       return true
217:     end
process(wait=nil, &block) click to toggle source

The core of the event loop. It processes a single iteration of the event loop. If a block is given, it should return false when the processing should abort, which causes # to return false. Otherwise, # returns true. The session itself is yielded to the block as its only argument.

If wait is nil (the default), this method will block until any of the monitored IO objects are ready to be read from or written to. If you want it to not block, you can pass 0, or you can pass any other numeric value to indicate that it should block for no more than that many seconds. Passing 0 is a good way to poll the connection, but if you do it too frequently it can make your CPU quite busy!

This will also cause all active channels to be processed once each (see Net::SSH::Connection::Channel#on_process).

  # process multiple Net::SSH connections in parallel
  connections = [
    Net::SSH.start("host1", ...),
    Net::SSH.start("host2", ...)
  ]

  connections.each do |ssh|
    ssh.exec "grep something /in/some/files"
  end

  condition = Proc.new { |s| s.busy? }

  loop do
    connections.delete_if { |ssh| !ssh.process(0.1, &condition) }
    break if connections.empty?
  end
     # File lib/net/ssh/connection/session.rb, line 196
196:     def process(wait=nil, &block)
197:       return false unless preprocess(&block)
198: 
199:       r = listeners.keys
200:       w = r.select { |w2| w2.respond_to?(:pending_write?) && w2.pending_write? }
201:       readers, writers, = Net::SSH::Compat.io_select(r, w, nil, wait)
202: 
203:       postprocess(readers, writers)
204:     end
send_global_request(type, *extra, &callback) click to toggle source

Send a global request of the given type. The extra parameters must be even in number, and conform to the same format as described for Net::SSH::Buffer.from. If a callback is not specified, the request will not require a response from the server, otherwise the server is required to respond and indicate whether the request was successful or not. This success or failure is indicated by the callback being invoked, with the first parameter being true or false (success, or failure), and the second being the packet itself.

Generally, Net::SSH will manage global requests that need to be sent (e.g. port forward requests and such are handled in the Net::SSH::Service::Forward class, for instance). However, there may be times when you need to send a global request that isn’t explicitly handled by Net::SSH, and so this method is available to you.

  ssh.send_global_request("keep-alive@openssh.com")
     # File lib/net/ssh/connection/session.rb, line 260
260:     def send_global_request(type, *extra, &callback)
261:       info { "sending global request #{type}" }
262:       msg = Buffer.from(:byte, GLOBAL_REQUEST, :string, type.to_s, :bool, !callback.nil?, *extra)
263:       send_message(msg)
264:       pending_requests << callback if callback
265:       self
266:     end
send_message(message) click to toggle source

Enqueues a message to be sent to the server as soon as the socket is available for writing. Most programs will never need to call this, but if you are implementing an extension to the SSH protocol, or if you need to send a packet that Net::SSH does not directly support, you can use this to send it.

 ssh.send_message(Buffer.from(:byte, REQUEST_SUCCESS).to_s)
     # File lib/net/ssh/connection/session.rb, line 367
367:     def send_message(message)
368:       transport.enqueue_message(message)
369:     end
shutdown!() click to toggle source

Performs a “hard” shutdown of the connection. In general, this should never be done, but it might be necessary (in a rescue clause, for instance, when the connection needs to close but you don’t know the status of the underlying protocol’s state).

     # File lib/net/ssh/connection/session.rb, line 118
118:     def shutdown!
119:       transport.shutdown!
120:     end
stop_listening_to(io) click to toggle source

Removes the given io object from the listeners collection, so that the event loop will no longer monitor it.

     # File lib/net/ssh/connection/session.rb, line 411
411:     def stop_listening_to(io)
412:       listeners.delete(io)
413:     end

Private Instance Methods

channel_close(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 569
569:       def channel_close(packet)
570:         info { "channel_close: #{packet[:local_id]}" }
571: 
572:         channel = channels[packet[:local_id]]
573:         channel.close
574: 
575:         channels.delete(packet[:local_id])
576:         channel.do_close
577:       end
channel_data(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 554
554:       def channel_data(packet)
555:         info { "channel_data: #{packet[:local_id]} #{packet[:data].length}b" }
556:         channels[packet[:local_id]].do_data(packet[:data])
557:       end
channel_eof(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 564
564:       def channel_eof(packet)
565:         info { "channel_eof: #{packet[:local_id]}" }
566:         channels[packet[:local_id]].do_eof
567:       end
channel_extended_data(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 559
559:       def channel_extended_data(packet)
560:         info { "channel_extended_data: #{packet[:local_id]} #{packet[:data_type]} #{packet[:data].length}b" }
561:         channels[packet[:local_id]].do_extended_data(packet[:data_type], packet[:data])
562:       end
channel_failure(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 584
584:       def channel_failure(packet)
585:         info { "channel_failure: #{packet[:local_id]}" }
586:         channels[packet[:local_id]].do_failure
587:       end
channel_open(packet) click to toggle source

Called when the server wants to open a channel. If no registered channel handler exists for the given channel type, CHANNEL_OPEN_FAILURE is returned, otherwise the callback is invoked and everything proceeds accordingly.

     # File lib/net/ssh/connection/session.rb, line 502
502:       def channel_open(packet)
503:         info { "channel open #{packet[:channel_type]}" }
504: 
505:         local_id = get_next_channel_id
506:         channel = Channel.new(self, packet[:channel_type], local_id)
507:         channel.do_open_confirmation(packet[:remote_id], packet[:window_size], packet[:packet_size])
508: 
509:         callback = channel_open_handlers[packet[:channel_type]]
510: 
511:         if callback
512:           begin
513:             callback[self, channel, packet]
514:           rescue ChannelOpenFailed => err
515:             failure = [err.code, err.reason]
516:           else
517:             channels[local_id] = channel
518:             msg = Buffer.from(:byte, CHANNEL_OPEN_CONFIRMATION, :long, channel.remote_id, :long, channel.local_id, :long, channel.local_maximum_window_size, :long, channel.local_maximum_packet_size)
519:           end
520:         else
521:           failure = [3, "unknown channel type #{channel.type}"]
522:         end
523: 
524:         if failure
525:           error { failure.inspect }
526:           msg = Buffer.from(:byte, CHANNEL_OPEN_FAILURE, :long, channel.remote_id, :long, failure[0], :string, failure[1], :string, "")
527:         end
528: 
529:         send_message(msg)
530:       end
channel_open_confirmation(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 532
532:       def channel_open_confirmation(packet)
533:         info { "channel_open_confirmation: #{packet[:local_id]} #{packet[:remote_id]} #{packet[:window_size]} #{packet[:packet_size]}" }
534:         channel = channels[packet[:local_id]]
535:         channel.do_open_confirmation(packet[:remote_id], packet[:window_size], packet[:packet_size])
536:       end
channel_open_failure(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 538
538:       def channel_open_failure(packet)
539:         error { "channel_open_failed: #{packet[:local_id]} #{packet[:reason_code]} #{packet[:description]}" }
540:         channel = channels.delete(packet[:local_id])
541:         channel.do_open_failed(packet[:reason_code], packet[:description])
542:       end
channel_request(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 549
549:       def channel_request(packet)
550:         info { "channel_request: #{packet[:local_id]} #{packet[:request]} #{packet[:want_reply]}" }
551:         channels[packet[:local_id]].do_request(packet[:request], packet[:want_reply], packet[:request_data])
552:       end
channel_success(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 579
579:       def channel_success(packet)
580:         info { "channel_success: #{packet[:local_id]}" }
581:         channels[packet[:local_id]].do_success
582:       end
channel_window_adjust(packet) click to toggle source
     # File lib/net/ssh/connection/session.rb, line 544
544:       def channel_window_adjust(packet)
545:         info { "channel_window_adjust: #{packet[:local_id]} +#{packet[:extra_bytes]}" }
546:         channels[packet[:local_id]].do_window_adjust(packet[:extra_bytes])
547:       end
dispatch_incoming_packets() click to toggle source

Read all pending packets from the connection and dispatch them as appropriate. Returns as soon as there are no more pending packets.

     # File lib/net/ssh/connection/session.rb, line 450
450:       def dispatch_incoming_packets
451:         while packet = transport.poll_message
452:           unless MAP.key?(packet.type)
453:             raise Net::SSH::Exception, "unexpected response #{packet.type} (#{packet.inspect})"
454:           end
455: 
456:           send(MAP[packet.type], packet)
457:         end
458:       end
get_next_channel_id() click to toggle source

Returns the next available channel id to be assigned, and increments the counter.

     # File lib/net/ssh/connection/session.rb, line 462
462:       def get_next_channel_id
463:         @channel_id_counter += 1
464:       end
global_request(packet) click to toggle source

Invoked when a global request is received. The registered global request callback will be invoked, if one exists, and the necessary reply returned.

     # File lib/net/ssh/connection/session.rb, line 469
469:       def global_request(packet)
470:         info { "global request received: #{packet[:request_type]} #{packet[:want_reply]}" }
471:         callback = @on_global_request[packet[:request_type]]
472:         result = callback ? callback.call(packet[:request_data], packet[:want_reply]) : false
473: 
474:         if result != :sent && result != true && result != false
475:           raise "expected global request handler for `#{packet[:request_type]}' to return true, false, or :sent, but got #{result.inspect}"
476:         end
477: 
478:         if packet[:want_reply] && result != :sent
479:           msg = Buffer.from(:byte, result ? REQUEST_SUCCESS : REQUEST_FAILURE)
480:           send_message(msg)
481:         end
482:       end
request_failure(packet) click to toggle source

Invokes the next pending request callback with false.

     # File lib/net/ssh/connection/session.rb, line 492
492:       def request_failure(packet)
493:         info { "global request failure" }
494:         callback = pending_requests.shift
495:         callback.call(false, packet) if callback
496:       end
request_success(packet) click to toggle source

Invokes the next pending request callback with true.

     # File lib/net/ssh/connection/session.rb, line 485
485:       def request_success(packet)
486:         info { "global request success" }
487:         callback = pending_requests.shift
488:         callback.call(true, packet) if callback
489:       end

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