class Net::SSH::Connection::Session

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 70
def initialize(transport, options={})
  self.logger = transport.logger
    
  @transport = transport
  @options = options
    
  @channel_id_counter = -1
  @channels = Hash.new(NilChannel.new(self))
  @listeners = { transport.socket => nil }
  @pending_requests = []
  @channel_open_handlers = {}
  @on_global_request = {}
  @properties = (options[:properties] || {}).dup
    
  @max_pkt_size = (options.key?(:max_pkt_size) ? options[:max_pkt_size] : 0x8000)
  @max_win_size = (options.key?(:max_win_size) ? options[:max_win_size] : 0x20000)
    
  @keepalive = Keepalive.new(self)
    
  @event_loop = options[:event_loop] || SingleSessionEventLoop.new
  @event_loop.register(self)
end

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 96
def [](key)
  @properties[key]
end

Sets a custom property for this instance.

# File lib/net/ssh/connection/session.rb, line 101
def []=(key, value)
  @properties[key] = value
end

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 154
def busy?(include_invisible=false)
  if include_invisible
    channels.any?
  else
    channels.any? { |id, ch| !ch[:invisible] }
  end
end

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 123
def close
  info { "closing remaining channels (#{channels.length} open)" }
  channels.each { |id, channel| channel.close }
  begin
    loop(0.1) { channels.any? }
  rescue Net::SSH::Disconnect
    raise unless channels.empty?
  end
  transport.close
end

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 116
def closed?
  transport.closed?
end

Returns the file descriptors the event loop should wait for read/write events, we also return the max wait

# File lib/net/ssh/connection/session.rb, line 255
def ev_do_calculate_rw_wait(wait)
  r = listeners.keys
  w = r.select { |w2| w2.respond_to?(:pending_write?) && w2.pending_write? }
  [r,w,io_select_wait(wait)]
end

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 270
def ev_do_handle_events(readers, writers)
  Array(readers).each do |reader|
    if listeners[reader]
      listeners[reader].call(reader)
    else
      if reader.fill.zero?
        reader.close
        stop_listening_to(reader)
      end
    end
  end
    
  Array(writers).each do |writer|
    writer.send_pending
  end
end

calls Net::SSH::Transport::Session#rekey_as_needed to allow the transport layer to rekey

# File lib/net/ssh/connection/session.rb, line 289
def ev_do_postprocess(was_events)
  @keepalive.send_as_needed(was_events)
  transport.rekey_as_needed
  true
end

Called by event loop to process available data before going to event multiplexing

# File lib/net/ssh/connection/session.rb, line 248
def ev_preprocess(&block)
  dispatch_incoming_packets(raise_disconnect_errors: false)
  each_channel { |id, channel| channel.process unless channel.local_closed? }
end

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 #loop) in order for the command to actually execute.

This is effectively identical to calling open_channel, 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 379
def exec(command, status: nil, &block)
  open_channel do |channel|
    channel.exec(command) do |ch, success|
      raise "could not execute command: #{command.inspect}" unless success
    
      if status
        channel.on_request("exit-status") do |ch2,data|
          status[:exit_code] = data.read_long
        end
    
        channel.on_request("exit-signal") do |ch2, data|
          status[:exit_signal] = data.read_long
        end
      end
    
      channel.on_data do |ch2, data|
        if block
          block.call(ch2, :stdout, data)
        else
          $stdout.print(data)
        end
      end
    
      channel.on_extended_data do |ch2, type, data|
        if block
          block.call(ch2, :stderr, data)
        else
          $stderr.print(data)
        end
      end
    end
  end
end

Same as exec, except this will block until the command finishes. Also, if no block is given, this will return all output (stdout and stderr) as a single string.

matches = ssh.exec!("grep something /some/files")

the returned string has an exitstatus method to query it's exit satus

# File lib/net/ssh/connection/session.rb, line 420
def exec!(command, status: nil, &block)
  block_or_concat = block || Proc.new do |ch, type, data|
    ch[:result] ||= ""
    ch[:result] << data
  end
    
  status ||= {}
  channel = exec(command, status: status, &block_or_concat)
  channel.wait
    
  channel[:result] ||= "" unless block
  channel[:result] &&= channel[:result].force_encoding("UTF-8") unless block
    
  StringWithExitstatus.new(channel[:result], status[:exit_code]) if channel[:result]
end

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 493
def forward
  @forward ||= Service::Forward.new(self)
end

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

# File lib/net/ssh/connection/session.rb, line 107
def host
  transport.host
end

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 fill method invoked.

Any io value passed to this method must have mixed into it the Net::SSH::BufferedIo functionality, typically by calling extend 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 481
def listen_to(io, &callback)
  listeners[io] = callback
end

The main event loop. Calls process until process returns false. If a block is given, it is passed to process, otherwise a default proc is used that just returns true if there are any channels active (see busy?). The # wait parameter is also passed through to process (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 179
def loop(wait=nil, &block)
  running = block || Proc.new { busy? }
  loop_forever { break unless process(wait, &running) }
  begin
    process(0)
  rescue IOError => e
    if e.message =~ /closed/
      debug { "stream was closed after loop => shallowing exception so it will be re-raised in next loop" }
    else
      raise
    end
  end
end

If the preprocess and postprocess callbacks for this session need to run periodically, this method returns the maximum number of seconds which may pass between callbacks.

# File lib/net/ssh/connection/session.rb, line 532
def max_select_wait_time
  @keepalive.interval if @keepalive.enabled?
end

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 517
def on_global_request(type, &block)
  old, @on_global_request[type] = @on_global_request[type], block
  old
end

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 507
def on_open_channel(type, &block)
  channel_open_handlers[type] = block
end

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 open_channel 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 338
def open_channel(type="session", *extra, &on_confirm)
  local_id = get_next_channel_id
    
  channel = Channel.new(self, type, local_id, @max_pkt_size, @max_win_size, &on_confirm)
  msg = Buffer.from(:byte, CHANNEL_OPEN, :string, type, :long, local_id,
    :long, channel.local_maximum_window_size,
    :long, channel.local_maximum_packet_size, *extra)
  send_message(msg)
    
  channels[local_id] = channel
end

This is called internally as part of process.

# File lib/net/ssh/connection/session.rb, line 262
def postprocess(readers, writers)
  ev_do_handle_events(readers, writers)
end

This is called internally as part of process. 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 239
def preprocess(&block)
  return false if block_given? && !yield(self)
  ev_preprocess(&block)
  return false if block_given? && !yield(self)
  return true
end

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 process to return false. Otherwise, process 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).

TODO revise example

# 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 227
def process(wait=nil, &block)
  @event_loop.process(wait, &block)
rescue StandardError
  force_channel_cleanup_on_close if closed?
  raise
end

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 311
def send_global_request(type, *extra, &callback)
  info { "sending global request #{type}" }
  msg = Buffer.from(:byte, GLOBAL_REQUEST, :string, type.to_s, :bool, !callback.nil?, *extra)
  send_message(msg)
  pending_requests << callback if callback
  self
end

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 443
def send_message(message)
  transport.enqueue_message(message)
end

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 138
def shutdown!
  transport.shutdown!
end

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 487
def stop_listening_to(io)
  listeners.delete(io)
end