Functions for communicating with sockets using the SCTP protocol.
This module provides functions for communicating with
sockets using the SCTP protocol. The implementation assumes that
the OS kernel supports SCTP
During development, this implementation was tested on:
- Linux Fedora Core 5.0 (kernel 2.6.15-2054 or later is needed)
- Solaris 10, 11
During OTP adaptation it was tested on:
- SUSE Linux Enterprise Server 10 (x86_64) kernel 2.6.16.27-0.6-smp, with lksctp-tools-1.0.6
- Briefly on Solaris 10
- SUSE Linux Enterprise Server 10 Service Pack 1 (x86_64) kernel 2.6.16.54-0.2.3-smp with lksctp-tools-1.0.7
- FreeBSD 8.2
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 this 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{}
,
which identifies an association for an SCTP socket. The term
is opaque except for the special value 0
, which 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} |
{tclass, integer() >= 0} |
{ttl, integer() >= 0} |
{recvtos, boolean()} |
{recvtclass, boolean()} |
{recvttl, boolean()}
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 |
tclass | ttl | recvtos | recvtclass | recvttl
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 specified by
, without
flushing of unsent data. The socket itself remains open. Other
associations opened on this socket are still valid, and the socket
can be used in new associations.
close(Socket) -> ok | {error, inet:posix()}
Socket = sctp_socket()
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 socket
,
with the peer (SCTP server socket) specified by
and
.
, 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
(that is, source address and port), as the controlling process
blocks until connect/*
returns.
connect_init/*
provides an alternative without this limitation.
The result of connect/*
is an #sctp_assoc_change{}
event that 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 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 stream numbers on the socket. These can be different
from the requested values (OutStreams
and MaxInStreams
,
respectively) if the peer requires lower values.
state
can have the following values:
comm_up
Association is successfully established. This
indicates a successful completion of connect
.
cant_assoc
The association cannot be established
(connect/*
failure).
Other states do not normally occur in the output from
connect/*
. Rather, they can occur in
#sctp_assoc_change{}
events received instead of data in
recv/*
calls.
All of them indicate losing the association because of various error
conditions, and are listed here for the sake of completeness:
comm_lost
restart
shutdown_comp
Field error
can provide more detailed diagnostics.
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 socket
,
with the peer (SCTP server socket) specified 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,
the result of the association establishment 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/*
,
except 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 | badarg | 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 specified by
, with
flushing of all unsent data. The socket itself remains open. Other
associations opened on this socket are still valid. The socket can
be used in new associations.
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 or undefined
for an unrecognized error.
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, there is no listening queue length in SCTP.
If
is true
, the socket accepts
new associations, that is, it becomes an SCTP server socket.
For type stream
, sockets
open() -> {ok, Socket} | {error, inet:posix()}
Socket = sctp_socket()
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
free port.
Other options:
inet6
Sets up the socket for IPv6.
inet
Sets 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.
If the socket is in
passive
mode data can be received through the
recv/1,2
calls.
If the socket is in active mode data received data is delivered to the controlling process as messages:
{sctp,Socket , FromIP, FromPort, {AncData, Data}}
See
recv/1,2
for a description of the message fields.
peeloff(Socket, Assoc) -> {ok, NewSocket} | {error, Reason}
Socket = sctp_socket()
Assoc = #sctp_assoc_change{} | assoc_id()
NewSocket = sctp_socket()
Reason = term()
Branches off an existing association
in a socket
of type seqpacket
(one-to-many style) into
a new socket
of type stream
(one-to-one style).
The existing association argument
can be either a
#sctp_assoc_change{}
record as returned from, for example,
recv/*
,
connect/*
, or
from a listening socket in active mode. It can also be just
the field 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{} | inet:ancillary_data()]
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{} | inet:ancillary_data()]
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 time-out is infinity
.
and
indicate the address of the
sender.
is a list of ancillary data items that
can 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, as such ancillary data
provides an easy way of determining the association and stream
over which the message is received.
(An alternative way is to get the association ID from
and
using
socket option
sctp_get_peer_addr_info
,
but this does still not produce the stream number).
may also contain
ancillary data
from the socket
options
recvtos
,
recvtclass
or
recvttl
,
if that is supported by the platform for the socket.
The
received can be a binary()
or a list()
of bytes (integers in the range 0 through 255)
depending on the socket mode, or an SCTP event.
Possible SCTP events:
-
#sctp_sndrcvinfo{}
-
#sctp_assoc_change{}
-
#sctp_paddr_change{ addr = {ip_address(),port()}, state = atom(), error = integer(), assoc_id = assoc_id() }
Indicates change of the status of the IP address of the peer specified by
addr
within 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 (for example,
addr_unreachable
), fielderror
provides more diagnostics. In such cases, event#sctp_paddr_change{}
is automatically converted into anerror
term returned byrecv
. 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 can receive this event if a send operation fails.
flags
A Boolean specifying if the data has been transmitted over the wire.
error
Provides extended diagnostics, use
error_string/1
.info
The original
#sctp_sndrcvinfo{}
record used in the failedsend/*
.data
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 option
sctp_adaptation_layer
). Notice 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 function send/4
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 a
message over an existing association
and specified stream.
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 options listed here are allowed
for SCTP sockets. Options can be set on the socket using
open/1,2
or
inet:setopts/2
,
retrieved using
inet:getopts/2
.
Options can be changed when calling
connect/4,5
.
{mode, list|binary}
or just list
or binary
Determines the type of data returned from
recv/1,2
.
{active, true|false|once|N}
-
If
false
(passive mode, the default), the caller must do an explicitrecv
call to retrieve the available data from the socket. -
If
true|once|N
(active modes) received data or events are sent to the owning process. Seeopen/0..2
for the message format. -
If
true
(full active mode) there is no flow control.Note!
Note that this can cause the message queue to overflow causing for example the virtual machine to run out of memory and crash.
-
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 and 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), that number is added to the socket's counting of data messages to be delivered to the controlling process. If the result of the addition is negative, the count is set to0
. Once the count reaches0
, either through the delivery of messages or by being explicitly set withinet:setopts/2
, the socket mode is automatically reset to passive ({active, false}
). 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 callinet:setopts/2
to set the socket back into an active mode.
{tos, integer()}
Sets the Type-Of-Service field on the IP datagrams that are sent, to the specified value. This effectively determines a prioritization policy for the outbound packets. The acceptable values are system-dependent.
{priority, integer()}
A protocol-independent equivalent of tos
above. Setting
priority implies setting tos
as well.
{dontroute, true|false}
Defaults to false
. If true
, the kernel does not
send packets through any gateway, only sends them to directly
connected hosts.
{reuseaddr, true|false}
Defaults to false
. If true, the local binding address
{IP,Port}
of the socket can be reused immediately.
No waiting in state CLOSE_WAIT
is performed (can be
required for high-throughput servers).
{sndbuf, integer()}
The size, in bytes, of the OS 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 OS kernel receive buffer for this socket.
Sending errors would occur for datagrams larger than
val(recbuf)
. Setting this option also adjusts
the size of the driver buffer (see buffer
above).
{sctp_module, module()}
Overrides 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 retransmission time-out parameters, in milliseconds,
for the association(s) specified by assoc_id
.
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) specified 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 that this socket tries
to negotiate with its peer while establishing an association with it.
Is to 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
max_instreams
max_attempts
max_init_timeo
{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. This improves throughput at the expense of latency.
{sctp_disable_fragments, true|false}
If true
, induces an error on an attempt to send
a message larger than the current PMTU size
(which would require fragmentation/reassembling).
Notice 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 specified by assoc_id
,
{IP,Port}
must be one of the peer addresses.
This option determines that the specified address is treated by
the local SCTP stack as the primary address of the peer.
{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 to use {IP, Port}
as the primary address of the local endpoint for the association
specified by assoc_id
.
{sctp_adaptation_layer, #sctp_setadaptation{}}
#sctp_setadaptation{ adaptation_ind = integer() }
When set, requests that the local endpoint uses the value specified
by adaptation_ind
as the Adaptation Indication parameter for
establishing new associations. For details, 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()
Determines various per-address parameters for
the association specified by assoc_id
and the peer address
address
(the SCTP protocol supports multi-homing, so
more than one address can correspond to a specified association).
hbinterval
Heartbeat interval, in milliseconds
pathmaxrxt
Maximum number of retransmissions before this address is considered unreachable (and an alternative address is selected)
pathmtu
Fixed Path MTU, if automatic discovery is disabled (see
flags
below)
sackdelay
Delay, in milliseconds, for SAC messages (if the delay is
enabled, see flags
below)
flags
The following flags are available:
hb_enable
hb_disable
hb_demand
pmtud_enable
pmtud_disable
sackdelay_enable
sackdelay_disable
{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 default values for subsequent
send
calls on the association specified by
assoc_id
.
assoc_id = 0
(default) indicates
the whole endpoint.
The following fields typically must 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
addr_over
send
overwrites the primary peer addressabort
eof
Other fields are rarely used. For complete information, see
{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 (through
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
(specified by assoc_value
, in milliseconds) for
the specified 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 specified by assoc_id
.
The following are the
possible values of state
(the state designations are mostly
self-explanatory):
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
Semantics of the other fields:
sstat_rwnd
sstat_unackdata
sstat_penddata
sstat_instrms
sstat_outstrms
sstat_fragmentation_point
sstat_primary
#sctp_paddrinfo{}
){sctp_get_peer_addr_info, #sctp_paddrinfo{}}
#sctp_paddrinfo{ assoc_id = assoc_id(), address = {IP, Port}, state = inactive | active | unconfirmed, 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 address specified by address
within the association
specified by assoc_id
. Field address
fmust 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.
For the semantics of all fields, see
SCTP Examples
Example of an Erlang SCTP server that 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 interacting with the above server.
Notice that in this example the client creates an association with
the server with 5 outbound streams. Therefore, 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 that the corresponding event is 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 simple Erlang SCTP client that 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
gen_tcp(3)
,
gen_udp(3)
,
inet(3)
,