gen_sctp
The gen_sctp module provides functions for communicating with sockets using the SCTP protocol.
The gen_sctp
module provides functions for communicating with
sockets using the SCTP protocol. The implementation assumes that
the OS kernel supports SCTP
This module was written for one-to-many style sockets
(type seqpacket
). With the addition of
peeloff/2, one-to-one style
sockets (type stream
) were introduced.
Record definitions for the gen_sctp
module can be found using:
-include_lib("kernel/include/inet_sctp.hrl").
These record definitions use the "new" spelling 'adaptation', not the deprecated 'adaption', regardless of which spelling the underlying C API uses.
Types
assoc_id()
An opaque term returned in for example #sctp_paddr_change{}
that identifies an association for an SCTP socket. The term
is opaque except for the special value 0
that has a
meaning such as "the whole endpoint" or "all future associations".
option() =
{active, true | false | once | -32768..32767} |
{buffer, integer() >= 0} |
{dontroute, boolean()} |
{high_msgq_watermark, integer() >= 1} |
{linger, {boolean(), integer() >= 0}} |
{low_msgq_watermark, integer() >= 1} |
{mode, list | binary} |
list |
binary |
{priority, integer() >= 0} |
{recbuf, integer() >= 0} |
{reuseaddr, boolean()} |
{ipv6_v6only, boolean()} |
{sctp_adaptation_layer, #sctp_setadaptation{}} |
{sctp_associnfo, #sctp_assocparams{}} |
{sctp_autoclose, integer() >= 0} |
{sctp_default_send_param, #sctp_sndrcvinfo{}} |
{sctp_delayed_ack_time, #sctp_assoc_value{}} |
{sctp_disable_fragments, boolean()} |
{sctp_events, #sctp_event_subscribe{}} |
{sctp_get_peer_addr_info, #sctp_paddrinfo{}} |
{sctp_i_want_mapped_v4_addr, boolean()} |
{sctp_initmsg, #sctp_initmsg{}} |
{sctp_maxseg, integer() >= 0} |
{sctp_nodelay, boolean()} |
{sctp_peer_addr_params, #sctp_paddrparams{}} |
{sctp_primary_addr, #sctp_prim{}} |
{sctp_rtoinfo, #sctp_rtoinfo{}} |
{sctp_set_peer_primary_addr, #sctp_setpeerprim{}} |
{sctp_status, #sctp_status{}} |
{sndbuf, integer() >= 0} |
{tos, integer() >= 0}
One of the SCTP Socket Options.
option_name() =
active |
buffer |
dontroute |
high_msgq_watermark |
linger |
low_msgq_watermark |
mode |
priority |
recbuf |
reuseaddr |
ipv6_v6only |
sctp_adaptation_layer |
sctp_associnfo |
sctp_autoclose |
sctp_default_send_param |
sctp_delayed_ack_time |
sctp_disable_fragments |
sctp_events |
sctp_get_peer_addr_info |
sctp_i_want_mapped_v4_addr |
sctp_initmsg |
sctp_maxseg |
sctp_nodelay |
sctp_peer_addr_params |
sctp_primary_addr |
sctp_rtoinfo |
sctp_set_peer_primary_addr |
sctp_status |
sndbuf |
tos
sctp_socket()
Socket identifier returned from open/*
.
Functions
abort(Socket, Assoc) -> ok | {error, inet:posix()}
Socket = sctp_socket()
Assoc = #sctp_assoc_change{}
Abnormally terminates the association given by
, without
flushing of unsent data. The socket itself remains open. Other
associations opened on this socket are still valid, and it can be
used in new associations.
close(Socket) -> ok | {error, inet:posix()}
Socket = sctp_socket()
Completely closes the socket and all associations on it. The unsent
data is flushed as in eof/2
. The close/1
call
is blocking or otherwise depending of the value of
the linger socket
option.
If close
does not linger or linger timeout expires,
the call returns and the data is flushed in the background.
connect(Socket, Addr, Port, Opts) ->
{ok, Assoc} | {error, inet:posix()}
Socket = sctp_socket()
Addr = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Opts = [Opt :: option()]
Assoc = #sctp_assoc_change{}
Same as connect(
.
connect(Socket, Addr, Port, Opts, Timeout) ->
{ok, Assoc} | {error, inet:posix()}
Socket = sctp_socket()
Addr = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Opts = [Opt :: option()]
Timeout = timeout()
Assoc = #sctp_assoc_change{}
Establishes a new association for the socket
,
with the peer (SCTP server socket) given by
and
. The
,
is expressed in milliseconds. A socket can be associated with multiple peers.
WARNING:Using a value of
less than
the maximum time taken by the OS to establish an association (around 4.5 minutes
if the default values from RFC 4960 are used) can result in
inconsistent or incorrect return values. This is especially
relevant for associations sharing the same
(i.e. source address and port) since the controlling process
blocks until connect/*
returns.
connect_init/*
provides an alternative not subject to this limitation.
The result of connect/*
is an #sctp_assoc_change{}
event which contains, in particular, the new
Association ID.
#sctp_assoc_change{ state = atom(), error = atom(), outbound_streams = integer(), inbound_streams = integer(), assoc_id = assoc_id() }
The number of outbound and inbound streams can be set by
giving an sctp_initmsg
option to connect
as in:
connect(Socket , Ip,Port , [{sctp_initmsg,#sctp_initmsg{num_ostreams=OutStreams, max_instreams=MaxInStreams}}])
All options
are set on the socket before the
association is attempted. If an option record has got undefined
field values, the options record is first read from the socket
for those values. In effect,
option records only
define field values to change before connecting.
The returned outbound_streams
and inbound_streams
are the actual stream numbers on the socket, which may be different
from the requested values (OutStreams
and MaxInStreams
respectively) if the peer requires lower values.
The following values of state
are possible:
-
comm_up
: association successfully established. This indicates a successful completion ofconnect
. -
cant_assoc
: association cannot be established (connect/*
failure).
All other states do not normally occur in the output from
connect/*
. Rather, they may occur in
#sctp_assoc_change{}
events received instead of data in
recv/* calls.
All of them indicate losing the association due to various
error conditions, and are listed here for the sake of completeness.
The error
field may provide more detailed diagnostics.
-
comm_lost
; -
restart
; -
shutdown_comp
.
connect_init(Socket, Addr, Port, Opts) ->
ok | {error, inet:posix()}
Socket = sctp_socket()
Addr = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Opts = [option()]
Same as connect_init(
.
connect_init(Socket, Addr, Port, Opts, Timeout) ->
ok | {error, inet:posix()}
Socket = sctp_socket()
Addr = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Opts = [option()]
Timeout = timeout()
Initiates a new association for the socket
,
with the peer (SCTP server socket) given by
and
.
The fundamental difference between this API
and connect/*
is that the return value is that of the
underlying OS connect(2) system call. If ok
is returned
then the result of the association establishement is received
by the calling process as
an
#sctp_assoc_change{}
event. The calling process must be prepared to receive this, or
poll for it using recv/*
depending on the value of the
active option.
The parameters are as described
in connect/*, with the
exception of the
value.
The timer associated with
only supervises
IP resolution of
controlling_process(Socket, Pid) -> ok | {error, Reason}
Socket = sctp_socket()
Pid = pid()
Reason = closed | not_owner | inet:posix()
Assigns a new controlling process
to
. Same implementation
as gen_udp:controlling_process/2
.
eof(Socket, Assoc) -> ok | {error, Reason}
Socket = sctp_socket()
Assoc = #sctp_assoc_change{}
Reason = term()
Gracefully terminates the association given by
, with
flushing of all unsent data. The socket itself remains open. Other
associations opened on this socket are still valid, and it can be
used in new associations.
listen(Socket, IsServer) -> ok | {error, Reason}
listen(Socket, Backlog) -> ok | {error, Reason}
Socket = sctp_socket()
IsServer = boolean()
Reason = term()
Backlog = integer()
Sets up a socket to listen on the IP address and port number it is bound to.
For type seqpacket
sockets (the default)
must be true
or false
.
In contrast to TCP, in SCTP there is no listening queue length.
If
is true
the socket accepts new associations, i.e.
it will become an SCTP server socket.
For type stream
sockets
open() -> {ok, Socket} | {error, inet:posix()}
Socket = sctp_socket()
open(Port) -> {ok, Socket} | {error, inet:posix()}
open(Opts) -> {ok, Socket} | {error, inet:posix()}
Port = inet:port_number()
Socket = sctp_socket()
Opts = [Opt]
Opt =
{ip, IP} |
{ifaddr, IP} |
inet:address_family() |
{port, Port} |
{type, SockType} |
option()IP = inet:ip_address() | any | loopback
SockType = seqpacket | stream
open(Port, Opts) -> {ok, Socket} | {error, inet:posix()}
Opts = [Opt]
Opt =
{ip, IP} |
{ifaddr, IP} |
inet:address_family() |
{port, Port} |
{type, SockType} |
option()IP = inet:ip_address() | any | loopback
Port = inet:port_number()
SockType = seqpacket | stream
Socket = sctp_socket()
Creates an SCTP socket and binds it to the local addresses
specified by all {ip,
(or synonymously {ifaddr,
)
options (this feature is called SCTP multi-homing).
The default
and
are any
and 0
, meaning bind to all local addresses on any
one free port.
Other options are:
inet6
Set up the socket for IPv6.
inet
Set up the socket for IPv4. This is the default.
A default set of socket options
is used. In particular, the socket is opened in
binary and
passive mode,
with seqpacket
,
and with reasonably large
kernel and driver
buffers.
peeloff(Socket, Assoc) -> {ok, NewSocket} | {error, Reason}
Socket = sctp_socket()
Assoc = #sctp_assoc_change{} | assoc_id()
NewSocket = sctp_socket()
Reason = term()
Branch off an existing association seqpacket
(one-to-many style) into
a new socket stream
(one-to-one style).
The existing association argument assoc_id
integer from such a record.
recv(Socket) ->
{ok, {FromIP, FromPort, AncData, Data}} | {error, Reason}
Socket = sctp_socket()
FromIP = inet:ip_address()
FromPort = inet:port_number()
AncData = [#sctp_sndrcvinfo{}]
Data =
binary() |
string() |
#sctp_sndrcvinfo{} |
#sctp_assoc_change{} |
#sctp_paddr_change{} |
#sctp_adaptation_event{}Reason =
inet:posix() |
#sctp_send_failed{} |
#sctp_paddr_change{} |
#sctp_pdapi_event{} |
#sctp_remote_error{} |
#sctp_shutdown_event{}
recv(Socket, Timeout) ->
{ok, {FromIP, FromPort, AncData, Data}} | {error, Reason}
Socket = sctp_socket()
Timeout = timeout()
FromIP = inet:ip_address()
FromPort = inet:port_number()
AncData = [#sctp_sndrcvinfo{}]
Data =
binary() |
string() |
#sctp_sndrcvinfo{} |
#sctp_assoc_change{} |
#sctp_paddr_change{} |
#sctp_adaptation_event{}Reason =
inet:posix() |
#sctp_send_failed{} |
#sctp_paddr_change{} |
#sctp_pdapi_event{} |
#sctp_remote_error{} |
#sctp_shutdown_event{}
Receives the
message from any association of the socket.
If the receive times out {error,timeout
is returned.
The default timeout is infinity
.
and
indicate the sender's address.
is a list of Ancillary Data items which
may be received along with the main
.
This list can be empty, or contain a single
#sctp_sndrcvinfo{}
record, if receiving of such ancillary data is enabled
(see option
sctp_events).
It is enabled by default, since such ancillary data
provide an easy way of determining the association and stream
over which the message has been received.
(An alternative way would be to get the Association ID from the
and
using the
sctp_get_peer_addr_info socket option,
but this would still not produce the Stream number).
The actual
received may be a binary()
,
or list()
of bytes (integers in the range 0 through 255)
depending on the socket mode, or an SCTP Event.
The following SCTP Events are possible:
-
#sctp_paddr_change{ addr = {ip_address(),port()}, state = atom(), error = integer(), assoc_id = assoc_id() }
Indicates change of the status of the peer's IP address given by
addr
within the associationassoc_id
. Possible values ofstate
(mostly self-explanatory) include:-
addr_unreachable
; -
addr_available
; -
addr_removed
; -
addr_added
; -
addr_made_prim
. -
addr_confirmed
.
In case of an error (e.g.
addr_unreachable
), theerror
field provides additional diagnostics. In such cases, the#sctp_paddr_change{}
Event is automatically converted into anerror
term returned bygen_sctp:recv
. Theerror
field value can be converted into a string usingerror_string/1
. -
-
#sctp_send_failed{ flags = true | false, error = integer(), info = #sctp_sndrcvinfo{}, assoc_id = assoc_id() data = binary() }
The sender may receive this event if a send operation fails. The
flags
is a Boolean specifying whether the data have actually been transmitted over the wire;error
provides extended diagnostics, useerror_string/1
;info
is the original #sctp_sndrcvinfo{} record used in the failed send/*, anddata
is the whole original data chunk attempted to be sent.In the current implementation of the Erlang/SCTP binding, this Event is internally converted into an
error
term returned byrecv/*
. -
#sctp_adaptation_event{ adaptation_ind = integer(), assoc_id = assoc_id() }
Delivered when a peer sends an Adaptation Layer Indication parameter (configured through the option sctp_adaptation_layer). Note that with the current implementation of the Erlang/SCTP binding, this event is disabled by default.
-
#sctp_pdapi_event{ indication = sctp_partial_delivery_aborted, assoc_id = assoc_id() }
A partial delivery failure. In the current implementation of the Erlang/SCTP binding, this Event is internally converted into an
error
term returned byrecv/*
.
send(Socket, SndRcvInfo, Data) -> ok | {error, Reason}
Socket = sctp_socket()
SndRcvInfo = #sctp_sndrcvinfo{}
Data = binary() | iolist()
Reason = term()
Sends the
message with all sending parameters from a
#sctp_sndrcvinfo{} record.
This way, the user can specify the PPID (passed to the remote end)
and Context (passed to the local SCTP layer) which can be used
for example for error identification.
However, such a fine level of user control is rarely required.
The send/4 function is sufficient for most applications.
send(Socket, Assoc, Stream, Data) -> ok | {error, Reason}
Socket = sctp_socket()
Assoc = #sctp_assoc_change{} | assoc_id()
Stream = integer()
Data = binary() | iolist()
Reason = term()
Sends
message over an existing association and given
stream.
error_string(ErrorNumber) -> ok | string() | unknown_error
ErrorNumber = integer()
Translates an SCTP error number from for example
#sctp_remote_error{}
or #sctp_send_failed{}
into
an explanatory string, or one of the atoms ok
for no
error and undefined
for an unrecognized error.
SCTP SOCKET OPTIONS
The set of admissible SCTP socket options is by construction
orthogonal to the sets of TCP, UDP and generic INET options:
only those options which are explicitly listed below are allowed
for SCTP sockets. Options can be set on the socket using
gen_sctp:open/1,2
or inet:setopts/2
,
retrieved using inet:getopts/2
,
and when calling gen_sctp:connect/4,5
options can be changed.
{mode, list|binary}
or just list
or binary
Determines the type of data returned from gen_sctp:recv/1,2
.
{active, true|false|once|N}
-
If
false
(passive mode, the default), the caller needs to do an explicitgen_sctp:recv
call in order to retrieve the available data from the socket. -
If
true
(full active mode), the pending data or events are sent to the owning process.NB: This can cause the message queue to overflow, as there is no way to throttle the sender in this case (no flow control!).
-
If
once
, only one message is automatically placed in the message queue, and after that the mode is automatically reset to passive. This provides flow control as well as the possibility for the receiver to listen for its incoming SCTP data interleaved with other inter-process messages. -
If
active
is specified as an integerN
in the range -32768 to 32767 (inclusive), then that number is added to the socket's count of the number of data messages to be delivered to the controlling process. If the result of the addition would be negative, the count is set to 0. Once the count reaches 0, either through the delivery of messages or by being explicitly set with inet:setopts/2, the socket's mode is automatically reset to passive ({active, false}
) mode. When a socket in this active mode transitions to passive mode, the message{sctp_passive, Socket}
is sent to the controlling process to notify it that if it wants to receive more data messages from the socket, it must call inet:setopts/2 to set the socket back into an active mode.
{tos, integer()}
Sets the Type-Of-Service field on the IP datagrams being sent, to the given value, which effectively determines a prioritization policy for the outbound packets. The acceptable values are system-dependent. TODO: we do not provide symbolic names for these values yet.
{priority, integer()}
A protocol-independent equivalent of tos
above. Setting
priority implies setting tos as well.
{dontroute, true|false}
By default false
. If true
, the kernel does not
send packets via any gateway, only sends them to directly
connected hosts.
{reuseaddr, true|false}
By default false
. If true, the local binding address
{IP,Port}
of the socket can be re-used immediately:
no waiting in the CLOSE_WAIT state is performed (may be
required for high-throughput servers).
{sndbuf, integer()}
The size, in bytes, of the *kernel* send buffer for this socket.
Sending errors would occur for datagrams larger than
val(sndbuf)
. Setting this option also adjusts
the size of the driver buffer (see buffer
above).
{recbuf, integer()}
The size, in bytes, of the *kernel* recv buffer for this socket.
Sending errors would occur for datagrams larger than
val(sndbuf)
. Setting this option also adjusts
the size of the driver buffer (see buffer
above).
{sctp_module, module()}
Override which callback module is used. Defaults to
inet_sctp
for IPv4 and inet6_sctp
for IPv6.
{sctp_rtoinfo, #sctp_rtoinfo{}}
#sctp_rtoinfo{ assoc_id = assoc_id(), initial = integer(), max = integer(), min = integer() }
Determines re-transmission time-out parameters, in milliseconds,
for the association(s) given by assoc_id
.
If assoc_id = 0
(default) indicates the whole endpoint. See
{sctp_associnfo, #sctp_assocparams{}}
#sctp_assocparams{ assoc_id = assoc_id(), asocmaxrxt = integer(), number_peer_destinations = integer(), peer_rwnd = integer(), local_rwnd = integer(), cookie_life = integer() }
Determines association parameters for the association(s) given by
assoc_id
. assoc_id = 0
(default) indicates
the whole endpoint. See
{sctp_initmsg, #sctp_initmsg{}}
#sctp_initmsg{ num_ostreams = integer(), max_instreams = integer(), max_attempts = integer(), max_init_timeo = integer() }
Determines the default parameters which this socket attempts
to negotiate with its peer while establishing an association with it.
Should be set after open/*
but before the first
connect/*
. #sctp_initmsg{}
can also be used
as ancillary data with the first call of send/*
to
a new peer (when a new association is created).
-
num_ostreams
: number of outbound streams; -
max_instreams
: max number of in-bound streams; -
max_attempts
: max re-transmissions while establishing an association; -
max_init_timeo
: time-out in milliseconds for establishing an association.
{sctp_autoclose, integer() >= 0}
Determines the time (in seconds) after which an idle association is
automatically closed. 0
means that the association is
never automatically closed.
{sctp_nodelay, true|false}
Turns on|off the Nagle algorithm for merging small packets into larger ones (which improves throughput at the expense of latency).
{sctp_disable_fragments, true|false}
If true
, induces an error on an attempt to send
a message which is larger than the current PMTU size
(which would require fragmentation/re-assembling).
Note that message fragmentation does not affect
the logical atomicity of its delivery; this option
is provided for performance reasons only.
{sctp_i_want_mapped_v4_addr, true|false}
Turns on|off automatic mapping of IPv4 addresses into IPv6 ones (if the socket address family is AF_INET6).
{sctp_maxseg, integer()}
Determines the maximum chunk size if message fragmentation is used.
If 0
, the chunk size is limited by the Path MTU only.
{sctp_primary_addr, #sctp_prim{}}
#sctp_prim{ assoc_id = assoc_id(), addr = {IP, Port} } IP = ip_address() Port = port_number()
For the association given by assoc_id
,
{IP,Port}
must be one of the peer's addresses.
This option determines that the given address is
treated by the local SCTP stack as the peer's primary address.
{sctp_set_peer_primary_addr, #sctp_setpeerprim{}}
#sctp_setpeerprim{ assoc_id = assoc_id(), addr = {IP, Port} } IP = ip_address() Port = port_number()
When set, informs the peer that it should use {IP, Port}
as the primary address of the local endpoint for the association
given by assoc_id
.
{sctp_adaptation_layer, #sctp_setadaptation{}}
#sctp_setadaptation{ adaptation_ind = integer() }
When set, requests that the local endpoint uses the value given by
adaptation_ind
as the Adaptation Indication parameter for
establishing new associations. See
{sctp_peer_addr_params, #sctp_paddrparams{}}
#sctp_paddrparams{ assoc_id = assoc_id(), address = {IP, Port}, hbinterval = integer(), pathmaxrxt = integer(), pathmtu = integer(), sackdelay = integer(), flags = list() } IP = ip_address() Port = port_number()
This option determines various per-address parameters for
the association given by assoc_id
and the peer address
address
(the SCTP protocol supports multi-homing,
so more than 1 address can correspond to a given association).
-
hbinterval
: heartbeat interval, in milliseconds; -
pathmaxrxt
: max number of retransmissions before this address is considered unreachable (and an alternative address is selected); -
pathmtu
: fixed Path MTU, if automatic discovery is disabled (seeflags
below); -
sackdelay
: delay in milliseconds for SAC messages (if the delay is enabled, seeflags
below); -
flags
: the following flags are available:-
hb_enable
: enable heartbeat; -
hb_disable
: disable heartbeat; -
hb_demand
: initiate heartbeat immediately; -
pmtud_enable
: enable automatic Path MTU discovery; -
pmtud_disable
: disable automatic Path MTU discovery; -
sackdelay_enable
: enable SAC delay; -
sackdelay_disable
: disable SAC delay.
-
{sctp_default_send_param, #sctp_sndrcvinfo{}}
#sctp_sndrcvinfo{ stream = integer(), ssn = integer(), flags = list(), ppid = integer(), context = integer(), timetolive = integer(), tsn = integer(), cumtsn = integer(), assoc_id = assoc_id() }
#sctp_sndrcvinfo{}
is used both in this socket option, and as
ancillary data while sending or receiving SCTP messages. When
set as an option, it provides a default values for subsequent
gen_sctp:send
calls on the association given by
assoc_id
. assoc_id = 0
(default) indicates
the whole endpoint. The following fields typically need
to be specified by the sender:
-
sinfo_stream
: stream number (0-base) within the association to send the messages through; -
sinfo_flags
: the following flags are recognised:-
unordered
: the message is to be sent unordered; -
addr_over
: the address specified ingen_sctp:send
overwrites the primary peer address; -
abort
: abort the current association without flushing any unsent data; -
eof
: gracefully shut down the current association, with flushing of unsent data.
Other fields are rarely used. See
RFC2960 andSockets API Extensions for SCTP for full information. -
{sctp_events, #sctp_event_subscribe{}}
#sctp_event_subscribe{ data_io_event = true | false, association_event = true | false, address_event = true | false, send_failure_event = true | false, peer_error_event = true | false, shutdown_event = true | false, partial_delivery_event = true | false, adaptation_layer_event = true | false }
This option determines which
SCTP Events are to be
received (via recv/*)
along with the data. The only
exception is data_io_event
which enables or disables
receiving of
#sctp_sndrcvinfo{}
ancillary data, not events.
By default, all flags except adaptation_layer_event
are
enabled, although sctp_data_io_event
and
association_event
are used by the driver itself and not
exported to the user level.
{sctp_delayed_ack_time, #sctp_assoc_value{}}
#sctp_assoc_value{ assoc_id = assoc_id(), assoc_value = integer() }
Rarely used. Determines the ACK time
(given by assoc_value
in milliseconds) for
the given association or the whole endpoint
if assoc_value = 0
(default).
{sctp_status, #sctp_status{}}
#sctp_status{ assoc_id = assoc_id(), state = atom(), rwnd = integer(), unackdata = integer(), penddata = integer(), instrms = integer(), outstrms = integer(), fragmentation_point = integer(), primary = #sctp_paddrinfo{} }
This option is read-only. It determines the status of
the SCTP association given by assoc_id
. Possible values of
state
follows. The state designations are mostly
self-explanatory. state_empty
is the default which means
that no other state is active:
-
sctp_state_empty
-
sctp_state_closed
-
sctp_state_cookie_wait
-
sctp_state_cookie_echoed
-
sctp_state_established
-
sctp_state_shutdown_pending
-
sctp_state_shutdown_sent
-
sctp_state_shutdown_received
-
sctp_state_shutdown_ack_sent
The semantics of other fields is the following:
-
sstat_rwnd
: the association peer's current receiver window size; -
sstat_unackdata
: number of unacked data chunks; -
sstat_penddata
: number of data chunks pending receipt; -
sstat_instrms
: number of inbound streams; -
sstat_outstrms
: number of outbound streams; -
sstat_fragmentation_point
: message size at which SCTP fragmentation will occur; -
sstat_primary
: information on the current primary peer address (see below for the format of#sctp_paddrinfo{}
).
{sctp_get_peer_addr_info, #sctp_paddrinfo{}}
#sctp_paddrinfo{ assoc_id = assoc_id(), address = {IP, Port}, state = inactive | active, cwnd = integer(), srtt = integer(), rto = integer(), mtu = integer() } IP = ip_address() Port = port_number()
This option is read-only. It determines the parameters specific to
the peer's address given by address
within the association
given by assoc_id
. The address
field must be set by the
caller; all other fields are filled in on return.
If assoc_id = 0
(default), the address
is automatically translated into the corresponding
association ID. This option is rarely used; see
SCTP EXAMPLES
-
Example of an Erlang SCTP Server which receives SCTP messages and prints them on the standard output:
-module(sctp_server). -export([server/0,server/1,server/2]). -include_lib("kernel/include/inet.hrl"). -include_lib("kernel/include/inet_sctp.hrl"). server() -> server(any, 2006). server([Host,Port]) when is_list(Host), is_list(Port) -> {ok, #hostent{h_addr_list = [IP|_]}} = inet:gethostbyname(Host), io:format("~w -> ~w~n", [Host, IP]), server([IP, list_to_integer(Port)]). server(IP, Port) when is_tuple(IP) orelse IP == any orelse IP == loopback, is_integer(Port) -> {ok,S} = gen_sctp:open(Port, [{recbuf,65536}, {ip,IP}]), io:format("Listening on ~w:~w. ~w~n", [IP,Port,S]), ok = gen_sctp:listen(S, true), server_loop(S). server_loop(S) -> case gen_sctp:recv(S) of {error, Error} -> io:format("SCTP RECV ERROR: ~p~n", [Error]); Data -> io:format("Received: ~p~n", [Data]) end, server_loop(S).
-
Example of an Erlang SCTP Client which interacts with the above Server. Note that in this example, the Client creates an association with the Server with 5 outbound streams. For this reason, sending of "Test 0" over Stream 0 succeeds, but sending of "Test 5" over Stream 5 fails. The client then
abort
s the association, which results in the corresponding Event being received on the Server side.-module(sctp_client). -export([client/0, client/1, client/2]). -include_lib("kernel/include/inet.hrl"). -include_lib("kernel/include/inet_sctp.hrl"). client() -> client([localhost]). client([Host]) -> client(Host, 2006); client([Host, Port]) when is_list(Host), is_list(Port) -> client(Host,list_to_integer(Port)), init:stop(). client(Host, Port) when is_integer(Port) -> {ok,S} = gen_sctp:open(), {ok,Assoc} = gen_sctp:connect (S, Host, Port, [{sctp_initmsg,#sctp_initmsg{num_ostreams=5}}]), io:format("Connection Successful, Assoc=~p~n", [Assoc]), io:write(gen_sctp:send(S, Assoc, 0, <<"Test 0">>)), io:nl(), timer:sleep(10000), io:write(gen_sctp:send(S, Assoc, 5, <<"Test 5">>)), io:nl(), timer:sleep(10000), io:write(gen_sctp:abort(S, Assoc)), io:nl(), timer:sleep(1000), gen_sctp:close(S).
-
A very simple Erlang SCTP Client which uses the connect_init API.
-module(ex3). -export([client/4]). -include_lib("kernel/include/inet.hrl"). -include_lib("kernel/include/inet_sctp.hrl"). client(Peer1, Port1, Peer2, Port2) when is_tuple(Peer1), is_integer(Port1), is_tuple(Peer2), is_integer(Port2) -> {ok,S} = gen_sctp:open(), SctpInitMsgOpt = {sctp_initmsg,#sctp_initmsg{num_ostreams=5}}, ActiveOpt = {active, true}, Opts = [SctpInitMsgOpt, ActiveOpt], ok = gen_sctp:connect(S, Peer1, Port1, Opts), ok = gen_sctp:connect(S, Peer2, Port2, Opts), io:format("Connections initiated~n", []), client_loop(S, Peer1, Port1, undefined, Peer2, Port2, undefined). client_loop(S, Peer1, Port1, AssocId1, Peer2, Port2, AssocId2) -> receive {sctp, S, Peer1, Port1, {_Anc, SAC}} when is_record(SAC, sctp_assoc_change), AssocId1 == undefined -> io:format("Association 1 connect result: ~p. AssocId: ~p~n", [SAC#sctp_assoc_change.state, SAC#sctp_assoc_change.assoc_id]), client_loop(S, Peer1, Port1, SAC#sctp_assoc_change.assoc_id, Peer2, Port2, AssocId2); {sctp, S, Peer2, Port2, {_Anc, SAC}} when is_record(SAC, sctp_assoc_change), AssocId2 == undefined -> io:format("Association 2 connect result: ~p. AssocId: ~p~n", [SAC#sctp_assoc_change.state, SAC#sctp_assoc_change.assoc_id]), client_loop(S, Peer1, Port1, AssocId1, Peer2, Port2, SAC#sctp_assoc_change.assoc_id); {sctp, S, Peer1, Port1, Data} -> io:format("Association 1: received ~p~n", [Data]), client_loop(S, Peer1, Port1, AssocId1, Peer2, Port2, AssocId2); {sctp, S, Peer2, Port2, Data} -> io:format("Association 2: received ~p~n", [Data]), client_loop(S, Peer1, Port1, AssocId1, Peer2, Port2, AssocId2); Other -> io:format("Other ~p~n", [Other]), client_loop(S, Peer1, Port1, AssocId1, Peer2, Port2, AssocId2) after 5000 -> ok end.
SEE ALSO
inet(3),
gen_tcp(3),
gen_udp(3),