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gen_sctp(3erl) | Erlang Module Definition | gen_sctp(3erl) |
NAME¶
gen_sctp - The gen_sctp module provides functions for communicating with sockets using the SCTP protocol.DESCRIPTION¶
The gen_sctp module provides functions for communicating with sockets using the SCTP protocol. The implementation assumes that the OS kernel supports SCTP (RFC2960) through the user-level Sockets API Extensions. During development this implementation was tested on Linux Fedora Core 5.0 (kernel 2.6.15-2054 or later is needed), and on 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, and later on 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, and later also on 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 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.
CONTENTS¶
- *
- DATA TYPES
- *
- EXPORTS
- *
- SCTP SOCKET OPTIONS
- *
- SCTP EXAMPLES
- *
- SEE ALSO
DATA 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/*.
EXPORTS¶
abort(Socket, Assoc) -> ok | {error, inet:posix()}
Types:
Socket = sctp_socket()
Assoc = #sctp_assoc_change{}
Abnormally terminates the association given by Assoc, 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()}
Types:
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()}
Types:
Socket = sctp_socket()
Addr = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Opts = [Opt :: option()]
Assoc = #sctp_assoc_change{}
Same as connect(Socket, Addr, Port, Opts, infinity).
connect(Socket, Addr, Port, Opts, Timeout) -> {ok, Assoc} | {error, inet:posix()}
Types:
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 Socket, with the peer (SCTP
server socket) given by Addr and Port. The Timeout, is
expressed in milliseconds. A socket can be associated with multiple peers.
WARNING: Using a value of Timeout 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
Socket (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.
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.
#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 Opt 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, Opt 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 of connect.
- *
- cant_assoc: association cannot be established (connect/* failure).
- *
- comm_lost;
- *
- restart;
- *
- shutdown_comp.
connect_init(Socket, Addr, Port, Opts) -> ok | {error, inet:posix()}
Types:
Socket = sctp_socket()
Addr = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Opts = [ option()]
Same as connect_init(Socket, Addr, Port, Opts, infinity).
connect_init(Socket, Addr, Port, Opts, Timeout) -> ok | {error, inet:posix()}
Types:
Socket = sctp_socket()
Addr = inet:ip_address() | inet:hostname()
Port = inet:port_number()
Opts = [ option()]
Timeout = timeout()
Initiates a new association for the socket Socket, with the peer (SCTP
server socket) given by Addr and Port.
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
Timeout value.
The timer associated with Timeout only supervises IP resolution of
Addr
controlling_process(Socket, Pid) -> ok | {error, Reason}
Types:
Socket = sctp_socket()
Pid = pid()
Reason = closed | not_owner | inet:posix()
Assigns a new controlling process Pid to Socket. Same
implementation as gen_udp:controlling_process/2.
eof(Socket, Assoc) -> ok | {error, Reason}
Types:
Socket = sctp_socket()
Assoc = #sctp_assoc_change{}
Reason = term()
Gracefully terminates the association given by Assoc, 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}
Types:
Socket = sctp_socket()
Backlog = integer()
Reason = term()
Sets up a socket to listen on the IP address and port number it is bound to.
For type seqpacket sockets (the default) IsServer must be
true or false. In contrast to TCP, in SCTP there is no listening
queue length. If IsServer is true the socket accepts new
associations, i.e. it will become an SCTP server socket.
For type stream sockets Backlog defines the backlog queue length just
like in TCP.
open() -> {ok, Socket} | {error, inet:posix()}
open(Port) -> {ok, Socket} | {error, inet:posix()}
open(Opts) -> {ok, Socket} | {error, inet:posix()}
open(Port, Opts) -> {ok, Socket} | {error, inet:posix()}
Types:
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()
| {ifaddr, IP}
| inet:address_family()
| {port, Port}
| {type, SockType}
| option()
Creates an SCTP socket and binds it to the local addresses specified by all
{ip,IP} (or synonymously {ifaddr,IP}) options (this feature is
called SCTP multi-homing). The default IP and Port are
any and 0, meaning bind to all local addresses on any one free
port.
Other options are:
A default set of socket options is used. In particular, the socket is
opened in binary and passive mode, with SockType
seqpacket, and with reasonably large kernel and driver
buffers.
- inet6:
- Set up the socket for IPv6.
- inet:
- Set up the socket for IPv4. This is the default.
peeloff(Socket, Assoc) -> {ok, NewSocket} | {error, Reason}
Types:
Socket = sctp_socket()
Assoc = #sctp_assoc_change{} | assoc_id()
NewSocket = sctp_socket()
Reason = term()
Branch off an existing association Assoc in a socket Socket of type
seqpacket (one-to-many style) into a new socket NewSocket of type
stream (one-to-one style).
The existing association argument Assoc can be either a #sctp_assoc_change{}
record as returned from e.g recv/*, connect/* or from a
listening socket in active mode. Or it can be just the field assoc_id
integer from such a record.
recv(Socket) -> {ok, {FromIP, FromPort, AncData, Data}} | {error, Reason}
recv(Socket, Timeout) -> {ok, {FromIP, FromPort, AncData, Data}} | {error, Reason}
Types:
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{}
| string()
| #sctp_sndrcvinfo{}
| #sctp_assoc_change{}
| #sctp_paddr_change{}
| #sctp_adaptation_event{}
| #sctp_send_failed{}
| #sctp_paddr_change{}
| #sctp_pdapi_event{}
| #sctp_remote_error{}
| #sctp_shutdown_event{}
Receives the Data message from any association of the socket. If the
receive times out {error,timeout is returned. The default timeout is
infinity. FromIP and FromPort indicate the sender's
address.
AncData is a list of Ancillary Data items which may be received along
with the main Data. 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 FromIP and FromPort using the
sctp_get_peer_addr_info socket option, but this would still not produce
the Stream number).
The actual Data 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_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 peer's IP address given by addr
within the association assoc_id. Possible values of state
(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), the error field
provides additional diagnostics. In such cases, the
#sctp_paddr_change{} Event is automatically converted into an
error term returned by gen_sctp:recv. The error field
value can be converted into a string using error_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, use error_string/1;
info is the original #sctp_sndrcvinfo{} record used in the
failed send/*, and data 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 by
recv/*.
- *
#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
by recv/*.
send(Socket, SndRcvInfo, Data) -> ok | {error, Reason}
Types:
Socket = sctp_socket()
SndRcvInfo = #sctp_sndrcvinfo{}
Data = binary() | iolist()
Reason = term()
Sends the Data 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}
Types:
Socket = sctp_socket()
Assoc = #sctp_assoc_change{} | assoc_id()
Stream = integer()
Data = binary() | iolist()
Reason = term()
Sends Data message over an existing association and given stream.
error_string(ErrorNumber) -> ok | string() | unknown_error
Types:
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 explicit gen_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 integer N 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 RFC2960 and Sockets API Extensions for SCTP
for the exact semantics of the fields values.
- {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 Sockets API Extensions for SCTP for the discussion of their semantics.
Rarely used.
- {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 RFC2960 and Sockets API Extenstions for SCTP for more
details.
- {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 (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: 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:sendcalls 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 in gen_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 and Sockets 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 RFC2960 and Sockets API Extensions for
SCTP for the semantics of all fields.
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 aborts 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(3erl), gen_tcp(3erl), gen_udp(3erl), RFC2960 (Stream Control Transmission Protocol), Sockets API Extensions for SCTP.kernel 3.0.3 | Ericsson AB |