# DRb::DRbProtocol (Module)

In: | drb/drb.rb

Module managing the underlying network protocol(s) used by drb.

By default, drb uses the DRbTCPSocket protocol. Other protocols can be defined. A protocol must define the following class methods:

      [open(uri, config)] Open a client connection to the server at +uri+,
                          using configuration +config+.  Return a protocol
                          instance for this connection.
      [open_server(uri, config)] Open a server listening at +uri+,
                                 using configuration +config+.  Return a
                                 protocol instance for this listener.
      [uri_option(uri, config)] Take a URI, possibly containing an option
                                component (e.g. a trailing '?param=val'),
                                and return a [uri, option] tuple.

All of these methods should raise a DRbBadScheme error if the URI does not identify the protocol they support (e.g. "druby:" for the standard Ruby protocol). This is how the DRbProtocol module, given a URI, determines which protocol implementation serves that protocol.

The protocol instance returned by open_server must have the following methods:

accept
  Accept a new connection to the server. Returns a protocol instance capable of communicating with the client.
close
  Close the server connection.
uri
  Get the URI for this server.

The protocol instance returned by open must have the following methods:

send_request (ref, msg_id, arg, b)
  Send a request to `ref` with the given message id and arguments. This is most easily implemented by calling DRbMessage.send_request, providing a stream that sits on top of the current protocol.
recv_reply
  Receive a reply from the server and return it as a [success-boolean, reply-value] pair. This is most easily implemented by calling DRb.recv_reply, providing a stream that sits on top of the current protocol.
alive?
  Is this connection still alive?
close
  Close this connection.

The protocol instance returned by open_server().accept() must have the following methods:

recv_request
  Receive a request from the client and return a [object, message, args, block] tuple. This is most easily implemented by calling DRbMessage.recv_request, providing a stream that sits on top of the current protocol.
send_reply(succ, result)
  Send a reply to the client. This is most easily implemented by calling DRbMessage.send_reply, providing a stream that sits on top of the current protocol.
close
  Close this connection.

A new protocol is registered with the DRbProtocol module using the add_protocol method.

For examples of other protocols, see DRbUNIXSocket in drb/unix.rb, and HTTP0 in sample/http0.rb and sample/http0serv.rb in the full drb distribution.

## Methods

add_protocol open open_server uri_option

## Public Instance methods

add_protocol(prot)

Add a new protocol to the DRbProtocol module.

[Source]

    # File drb/drb.rb, line 685
        def add_protocol(prot)
          @protocol.push(prot)
        end

open(uri, config, first=true)

Open a client connection to `uri` with the configuration `config`.

The DRbProtocol module asks each registered protocol in turn to try to open the URI. Each protocol signals that it does not handle that URIby raising a DRbBadScheme error. If no protocol recognises the URI, then a DRbBadURI error is raised. If a protocol accepts the URI, but an error occurs in opening it, a DRbConnError is raised.

[Source]

    # File drb/drb.rb, line 697
        def open(uri, config, first=true)
          @protocol.each do |prot|
            begin
              return prot.open(uri, config)
            rescue DRbBadScheme
            rescue DRbConnError
              raise($!)
            rescue
              raise(DRbConnError, "#{uri} - #{$!.inspect}")
            end
          end
          if first && (config[:auto_load] != false)
            auto_load(uri, config)
            return open(uri, config, false)
          end
          raise DRbBadURI, 'can\'t parse uri:' + uri
        end

open_server(uri, config, first=true)

Open a server listening for connections at `uri` with configuration `config`.

The DRbProtocol module asks each registered protocol in turn to try to open a server at the URI. Each protocol signals that it does not handle that URI by raising a DRbBadScheme error. If no protocol recognises the URI, then a DRbBadURI error is raised. If a protocol accepts the URI, but an error occurs in opening it, the underlying error is passed on to the caller.

[Source]

    # File drb/drb.rb, line 725
        def open_server(uri, config, first=true)
          @protocol.each do |prot|
            begin
              return prot.open_server(uri, config)
            rescue DRbBadScheme
            end
          end
          if first && (config[:auto_load] != false)
            auto_load(uri, config)
            return open_server(uri, config, false)
          end
          raise DRbBadURI, 'can\'t parse uri:' + uri
        end

uri_option(uri, config, first=true)

Parse `uri` into a [uri, option] pair.

The DRbProtocol module asks each registered protocol in turn to try to parse the URI. Each protocol signals that it does not handle that URI by raising a DRbBadScheme error. If no protocol recognises the URI, then a DRbBadURI error is raised.

[Source]

    # File drb/drb.rb, line 746
        def uri_option(uri, config, first=true)
          @protocol.each do |prot|
            begin
              uri, opt = prot.uri_option(uri, config)
              # opt = nil if opt == ''

              return uri, opt
            rescue DRbBadScheme
            end
          end
          if first && (config[:auto_load] != false)
            auto_load(uri, config)
            return uri_option(uri, config, false)
          end
          raise DRbBadURI, 'can\'t parse uri:' + uri
        end

[Validate]