erl_ext_dist.txt

OTP是开放电信平台的简称

	                <---------------- PORT2_RESP

	NAMES_REQ       ---------------->                   

	                <---------------- NAMES_RESP

	DUMP_REQ        ---------------->                   

	                <---------------- DUMP_RESP

	KILL_REQ        ---------------->

	                <---------------- KILL_RESP

	STOP_REQ        ---------------->

	                <---------------- STOP_OK_RESP

	                <---------------- STOP_NOTOK_RESP

3.1 Requests

Each request *_REQ is presided by a two byte length field. Thus, the
overall request format is:

    2        n
+--------+---------+
| Length | Request |
+--------+---------+

3.1.1 ALIVE_REQ         (97)

   1     2         n
+----+--------+----------+
| 97 | PortNo | NodeName |
+----+--------+----------+

where n = Length - 3

The connection created to the EPMD must be kept until the node is
not a distributed node any longer.


3.1.1.1 ALIVE2_REQ	(120)


[120, PortNo, NodeType, Protocol, DistrvsnRange, Nlen, NodeName, Elen, Extra]
PortNo = 2 bytes
NodeType = 1 byte (77 = normal erlang node, 72 hidden node (c-node) ...)
Protocol = 1 byte [0 = tcp/ip-v4, ... ]
DistrvsnRange = [Highestvsn, Lowestvsn] where Highestvsn = Lowestvsn = 2 byte
	for erts-4.6.x (OTP-R3)the vsn = 0
	for erts-4.7.x (OTP-R4)
Nlen = 2 bytes
NodeName = string ,length = Nlen
Elen = 2 bytes
Extra = string ,length = Elen


The connection created to the EPMD must be kept until the node is
not a distributed node any longer.


3.1.2  ALIVE_CLOSE_REQ  ()

The connection is simply closed by the client.

3.1.3 PORT_PLEASE_REQ   (112)

   1       n
+-----+----------+
| 112 | NodeName |
+-----+----------+

where n = Length - 1

3.1.3.1 PORT_PLEASE2_REQ   (122)

   1       n
+-----+----------+
| 122 | NodeName |
+-----+----------+

where n = Length - 1

3.1.4 NAMES_REQ         (110)

   1  
+-----+
| 110 |
+-----+

3.1.5 DUMP_REQ          (100)

   1  
+-----+
| 100 |
+-----+

3.1.6 KILL_REQ          (107)

   1  
+-----+
| 107 |
+-----+

3.1.7 STOP_REQ          (115)  (Not Used)

   1       n
+-----+----------+
| 115 | NodeName |
+-----+----------+

where n = Length - 1

The current implementation of Erlang does not care if the connection
to the EPMD is broken.

3.2 Responses

3.2.1 ALIVE_OK_RESP     (89)

   1       2
+----+----------+
| 89 | Creation |
+----+----------+

3.2.1.1 ALIVE2_RESP (121)

   1     1          2
+----+--------+-----------+
|121 | Result | Creation  |
+----+--------+-----------+

Result = 0 -> ok, Result > 0 -> error


3.2.2 ALIVE_NOTOK_RESP  ()

EPMD closed the connection.

3.2.3 PORT_OK_RESP      ()

    2
+--------+
| PortNo |
+--------+

3.2.4 PORT_NOTOK_RESP   ()

EPMD closed the connection.

3.2.4.1 PORT2_RESP      (119)

[119, Result] or
[119, Result, PortNo, NodeType, Protocol, DistrvsnRange, Nlen, 
	NodeName, Elen, Extra]
Result = 1 byte (0 = ok, >0 error)
NodeType = 1 byte ( 77 - normal Erlang node , 72 - hidden node ...)
PortNo = 2 byte
Protocol = 1 byte
DistrvsnRange = [Highestvsn, Lowestvsn] Highestvsn = Lowestvsn = 2 bytes
Nlen = 2 bytes
NodeName = string, length = Nlen
Elen = 2 bytes
Extra = string, length = Elen

If Result > 0, the packet only consists of [119, Result].

3.2.4 PORT_NOTOK_RESP   ()

EPMD closed the connection.


3.2.5 NAMES_RESP        ()

      4
+------------+-----------+
| EPMDPortNo | NodeInfo* |
+------------+-----------+

NodeInfo is a string written for each active node.
When all NodeInfo has been written the connection is
closed by EPMD.

NodeInfo is, as expressed in Erlang:

	io:format("name ~s at port ~p~n", [NodeName, Port]).

3.2.6 DUMP_RESP         ()

      4
+------------+-----------+
| EPMDPortNo | NodeInfo* |
+------------+-----------+

NodeInfo is a string written for each node kept in EPMD.
When all NodeInfo has been written the connection is
closed by EPMD.

NodeInfo is, as expressed in Erlang:

	io:format("active name     ~s at port ~p, fd = ~p ~n",
	          [NodeName, Port, Fd]).

or

	io:format("old/unused name ~s at port ~p, fd = ~p~n",
	          [NodeName, Port, Fd]).



3.2.7 KILL_RESP         ()

     2
+----------+
| OKString |
+----------+

where OKString is "OK".

3.2.8 STOP_OK_RESP      ()

     7
+----------+
| OKString |
+----------+

where OKString is "STOPPED".

3.2.9 STOP_NOTOK_RESP   ()

     7
+-----------+
| NOKString |
+-----------+

where NOKString is "NOEXIST".



4 The Erlang <-> Erlang distribution protocol

The distribution protocol can be divided into four (4) parts:

	1. Low level socket connection.

	2. Handshake, interchange node name and authenticate.

	3. Authentication (done by net_kernel).

	4. Connected. 
	
A node fetches the Port number of another node through the EPMD (at the
other host) in order to initiate a connection request.

3 and 4 are performed at the same level but the net_kernel disconnects the
other node if it communicates using an invalid cookie (after one (1) second).

4.1 Handshake

The handshake is discussed in detail in the internal documentation for 
the kernel (erlang) application.

4.2 Protocol between connected nodes

     4       1         n          m
+--------+------+------------+----------+
| Length | Type | ControlMsg |  Message |
+--------+------+------------+----------+

where:

	Length is equal to 1 + n + m

	Type is: 112 - pass through

	ControlMsg is a tuple passed using the external format of
	Erlang.

	Message is the message sent to another node using the '!'
	(in external format).
	But, Message is only passed in combination with a ControlMsg
	encoding a send ('!').

4.2.1 Pass through

The control message is a tuple, where the first element indicates
which distributed operation it encodes.

4.2.1.1 LINK

	{1, FromPid, ToPid}

4.2.1.2 SEND

	{2, Cookie, ToPid}

	Note: Message is sent as well.

4.2.1.3 EXIT

	{3, FromPid, ToPid, Reason}

4.2.1.4 UNLINK

	{4, FromPid, ToPid}

4.2.1.5 NODE_LINK

	{5}

4.2.1.6 REG_SEND

	{6, FromPid, Cookie, ToName}

	Note: Message is sent as well.

4.2.1.7 GROUP_LEADER

	{7, FromPid, ToPid}

4.2.1.8 EXIT2

	{8, FromPid, ToPid, Reason}

-----------------------------------------------
New Ctrlmessages for distrvsn = 1 (OTP R4)
-----------------------------------------------

4.3.1 SEND_TT

	{12, Cookie, ToPid, TraceToken}

	Note: Message is sent as well.

4.3.2 EXIT_TT

	{13, FromPid, ToPid, TraceToken, Reason}


4.3.3 REG_SEND_TT

	{16, FromPid, Cookie, ToName, TraceToken}

	Note: Message is sent as well.


4.3.4 EXIT2_TT

	{18, FromPid, ToPid, TraceToken, Reason}


-----------------------------------------------
New Ctrlmessages for distrvsn = 2
-----------------------------------------------

distrvsn 2 was never used.

-----------------------------------------------
New Ctrlmessages for distrvsn = 3 (OTP R5C)
-----------------------------------------------

None, but the version number was increased anyway.

-----------------------------------------------
New Ctrlmessages for distrvsn = 4 (OTP R6)
These are only recognized by Erlang nodes, not by hidden nodes.
-----------------------------------------------

4.4.1 MONITOR_P

	{19, FromPid, ToProc, Ref}

	FromPid = monitoring process
	ToProc = monitored process pid or name (atom)

4.4.2 DEMONITOR_P

	{20, FromPid, ToProc, Ref}
	We include the FromPid just in case we want to trace this.

	FromPid = monitoring process
	ToProc = monitored process pid or name (atom)

4.4.3 MONITOR_P_EXIT

	{21, FromProc, ToPid, Ref, Reason}

	FromProc = monitored process pid or name (atom)
	ToPid = monitoring process
	Reason = exit reason for the monitored process