Ejabberd Developers GuideAlexey Shchepin |
I can thoroughly recommend ejabberd for ease of setup – Kevin Smith, Current maintainer of the Psi project
ejabberd is a free and open source instant messaging server written in Erlang/OTP.
ejabberd is cross-platform, distributed, fault-tolerant, and based on open standards to achieve real-time communication.
ejabberd is designed to be a rock-solid and feature rich XMPP server.
ejabberd is suitable for small deployments, whether they need to be scalable or not, as well as extremely big deployments.
ejabberd is:
Moreover, ejabberd comes with a wide range of other state-of-the-art features:
A XMPP domain is served by one or more ejabberd nodes. These nodes can be run on different machines that are connected via a network. They all must have the ability to connect to port 4369 of all another nodes, and must have the same magic cookie (see Erlang/OTP documentation, in other words the file ~ejabberd/.erlang.cookie must be the same on all nodes). This is needed because all nodes exchange information about connected users, S2S connections, registered services, etc…
Each ejabberd node have following modules:
This module is the main router of XMPP packets on each node. It routes them based on their destinations domains. It has two tables: local and global routes. First, domain of packet destination searched in local table, and if it found, then the packet is routed to appropriate process. If no, then it searches in global table, and is routed to the appropriate ejabberd node or process. If it does not exists in either tables, then it sent to the S2S manager.
This module routes packets which have a destination domain equal to this server name. If destination JID has a non-empty user part, then it routed to the session manager, else it is processed depending on it’s content.
This module routes packets to local users. It searches for what user resource packet must be sent via presence table. If this resource is connected to this node, it is routed to C2S process, if it connected via another node, then the packet is sent to session manager on that node.
This module routes packets to other XMPP servers. First, it checks if an open S2S connection from the domain of the packet source to the domain of packet destination already exists. If it is open on another node, then it routes the packet to S2S manager on that node, if it is open on this node, then it is routed to the process that serves this connection, and if a connection does not exist, then it is opened and registered.
The external authentication script follows the erlang port driver API.
That script is supposed to do theses actions, in an infinite loop:
Example python script
#!/usr/bin/python
import sys
from struct import *
def from_ejabberd():
input_length = sys.stdin.read(2)
(size,) = unpack('>h', input_length)
return sys.stdin.read(size).split(':')
def to_ejabberd(bool):
answer = 0
if bool:
answer = 1
token = pack('>hh', 2, answer)
sys.stdout.write(token)
sys.stdout.flush()
def auth(username, server, password):
return True
def isuser(username, server):
return True
def setpass(username, server, password):
return True
while True:
data = from_ejabberd()
success = False
if data[0] == "auth":
success = auth(data[1], data[2], data[3])
elif data[0] == "isuser":
success = isuser(data[1], data[2])
elif data[0] == "setpass":
success = setpass(data[1], data[2], data[3])
to_ejabberd(success)
Each XML stanza is represented as the following tuple:
XMLElement = {xmlelement, Name, Attrs, [ElementOrCDATA]}
Name = string()
Attrs = [Attr]
Attr = {Key, Val}
Key = string()
Val = string()
ElementOrCDATA = XMLElement | CDATA
CDATA = {xmlcdata, string()}
E. g. this stanza:
<message to='test@conference.example.org' type='groupchat'> <body>test</body> </message>
is represented as the following structure:
{xmlelement, "message",
[{"to", "test@conference.example.org"},
{"type", "groupchat"}],
[{xmlelement, "body",
[],
[{xmlcdata, "test"}]}]}}
element_to_string(El) -> string()
El = XMLElementReturns string representation of XML stanza El.
crypt(S) -> string()
S = string()Returns string which correspond to S with encoded XML special characters.
remove_cdata(ECList) -> EList
ECList = [ElementOrCDATA] EList = [XMLElement]EList is a list of all non-CDATA elements of ECList.
get_path_s(El, Path) -> Res
El = XMLElement
Path = [PathItem]
PathItem = PathElem | PathAttr | PathCDATA
PathElem = {elem, Name}
PathAttr = {attr, Name}
PathCDATA = cdata
Name = string()
Res = string() | XMLElement
If Path is empty, then returns El. Else sequentially
consider elements of Path. Each element is one of:
{elem, Name} Name is name of subelement of
El, if such element exists, then this element considered in
following steps, else returns empty string.
{attr, Name} If El have attribute Name, then
returns value of this attribute, else returns empty string.
cdata Returns CDATA of El.
get_cdata/1, get_tag_cdata/1
get_attr/2, get_attr_s/2
get_tag_attr/2, get_tag_attr_s/2
get_subtag/2
parse_element(Str) -> XMLElement | {error, Err}
Str = string() Err = term()Parses Str using XML parser, returns either parsed element or error tuple.
The module gen_iq_handler allows to easily write handlers for IQ packets
of particular XML namespaces that addressed to server or to users bare JIDs.
In this module the following functions are defined:
add_iq_handler(Component, Host, NS, Module, Function, Type)
Component = Module = Function = atom() Host = NS = string() Type = no_queue | one_queue | parallelRegisters function
Module:Function as handler for IQ packets on
virtual host Host that contain child of namespace NS in
Component. Queueing discipline is Type. There are at least
two components defined:
ejabberd_local Handles packets that addressed to server JID;
ejabberd_sm Handles packets that addressed to users bare JIDs.
remove_iq_handler(Component, Host, NS)
Component = atom() Host = NS = string()Removes IQ handler on virtual host
Host for namespace NS from
Component.
Handler function must have the following type:
Module:Function(From, To, IQ)
From = To = jid()
-module(mod_cputime).
-behaviour(gen_mod).
-export([start/2,
stop/1,
process_local_iq/3]).
-include("ejabberd.hrl").
-include("jlib.hrl").
-define(NS_CPUTIME, "ejabberd:cputime").
start(Host, Opts) ->
IQDisc = gen_mod:get_opt(iqdisc, Opts, one_queue),
gen_iq_handler:add_iq_handler(ejabberd_local, Host, ?NS_CPUTIME,
?MODULE, process_local_iq, IQDisc).
stop(Host) ->
gen_iq_handler:remove_iq_handler(ejabberd_local, Host, ?NS_CPUTIME).
process_local_iq(From, To, {iq, ID, Type, XMLNS, SubEl}) ->
case Type of
set ->
{iq, ID, error, XMLNS,
[SubEl, ?ERR_NOT_ALLOWED]};
get ->
CPUTime = element(1, erlang:statistics(runtime))/1000,
SCPUTime = lists:flatten(io_lib:format("~.3f", CPUTime)),
{iq, ID, result, XMLNS,
[{xmlelement, "query",
[{"xmlns", ?NS_CPUTIME}],
[{xmlelement, "cputime", [], [{xmlcdata, SCPUTime}]}]}]}
end.
-module(mod_echo).
-behaviour(gen_mod).
-export([start/2, init/1, stop/1]).
-include("ejabberd.hrl").
-include("jlib.hrl").
start(Host, Opts) ->
MyHost = gen_mod:get_opt(host, Opts, "echo." ++ Host),
register(gen_mod:get_module_proc(Host, ?PROCNAME),
spawn(?MODULE, init, [MyHost])).
init(Host) ->
ejabberd_router:register_local_route(Host),
loop(Host).
loop(Host) ->
receive
{route, From, To, Packet} ->
ejabberd_router:route(To, From, Packet),
loop(Host);
stop ->
ejabberd_router:unregister_route(Host),
ok;
_ ->
loop(Host)
end.
stop(Host) ->
Proc = gen_mod:get_module_proc(Host, ?PROCNAME),
Proc ! stop,
{wait, Proc}.
This document was translated from LATEX by HEVEA.