| inet(3erl) | Erlang Module Definition | inet(3erl) |
inet - Access to TCP/IP protocols.
This module provides access to TCP/IP protocols.
See also ERTS User's Guide: Inet Configuration for more information about how to configure an Erlang runtime system for IP communication.
The following two Kernel configuration parameters affect the behavior of all sockets opened on an Erlang node:
When accept is issued, the values of the listening socket options are inherited. No such application variable is therefore needed for accept.
Using the Kernel configuration parameters above, one can set default options for all TCP sockets on a node, but use this with care. Options such as {delay_send,true} can be specified in this way. The following is an example of starting an Erlang node with all sockets using delayed send:
$ erl -sname test -kernel \
inet_default_connect_options '[{delay_send,true}]' \
inet_default_listen_options '[{delay_send,true}]'
Notice that default option {active, true} cannot be changed, for internal reasons.
Addresses as inputs to functions can be either a string or a tuple. For example, the IP address 150.236.20.73 can be passed to gethostbyaddr/1, either as string "150.236.20.73" or as tuple {150, 236, 20, 73}.
IPv4 address examples:
Address ip_address()
------- ------------
127.0.0.1 {127,0,0,1}
192.168.42.2 {192,168,42,2}
IPv6 address examples:
Address ip_address()
------- ------------
::1 {0,0,0,0,0,0,0,1}
::192.168.42.2 {0,0,0,0,0,0,(192 bsl 8) bor 168,(42 bsl 8) bor 2}
::FFFF:192.168.42.2
{0,0,0,0,0,16#FFFF,(192 bsl 8) bor 168,(42 bsl 8) bor 2}
3ffe:b80:1f8d:2:204:acff:fe17:bf38
{16#3ffe,16#b80,16#1f8d,16#2,16#204,16#acff,16#fe17,16#bf38}
fe80::204:acff:fe17:bf38
{16#fe80,0,0,0,16#204,16#acff,16#fe17,16#bf38}
Function parse_address/1 can be useful:
1> inet:parse_address("192.168.42.2").
{ok,{192,168,42,2}}
2> inet:parse_address("::FFFF:192.168.42.2").
{ok,{0,0,0,0,0,65535,49320,10754}}
hostent() =
#hostent{h_name = inet:hostname(),
h_aliases = [inet:hostname()],
h_addrtype = inet | inet6,
h_length = integer() >= 0,
h_addr_list = [inet:ip_address()]}
The record is defined in the Kernel include file "inet.hrl".
Add the following directive to the module:
-include_lib("kernel/include/inet.hrl").
hostname() = atom() | string()
ip_address() = ip4_address() | ip6_address()
ip4_address() = {0..255, 0..255, 0..255, 0..255}
ip6_address() =
{0..65535,
0..65535,
0..65535,
0..65535,
0..65535,
0..65535,
0..65535,
0..65535}
port_number() = 0..65535
family_address() =
inet_address() | inet6_address() | local_address()
A general address format on the form {Family, Destination} where Family is an atom such as local and the format of Destination depends on Family, and is a complete address (for example an IP address including port number).
inet_address() =
{inet, {ip4_address() | any | loopback, port_number()}}
inet6_address() =
{inet6, {ip6_address() | any | loopback, port_number()}}
local_address() = {local, File :: binary() | string()}
This address family only works on Unix-like systems.
File is normally a file pathname in a local filesystem. It is limited in length by the operating system, traditionally to 108 bytes.
A binary() is passed as is to the operating system, but a string() is encoded according to the system filename encoding mode.
Other addresses are possible, for example Linux implements "Abstract Addresses". See the documentation for Unix Domain Sockets on your system, normally unix in manual section 7.
In most API functions where you can use this address family the port number must be 0.
socket_address() =
ip_address() | any | loopback | local_address()
socket_getopt() =
gen_sctp:option_name() |
gen_tcp:option_name() |
gen_udp:option_name()
socket_setopt() =
gen_sctp:option() | gen_tcp:option() | gen_udp:option()
returned_non_ip_address() =
{local, binary()} | {unspec, <<>>} | {undefined, any()}
Addresses besides ip_address() ones that are returned from socket API functions. See in particular local_address(). The unspec family corresponds to AF_UNSPEC and can occur if the other side has no socket address. The undefined family can only occur in the unlikely event of an address family that the VM does not recognize.
ancillary_data() =
[{tos, byte()} | {tclass, byte()} | {ttl, byte()}]
Ancillary data received with the data packet, read with the socket option pktoptions from a TCP socket, or to set in a call to gen_udp:send/4 or gen_udp:send/5.
The value(s) correspond to the currently active socket options recvtos, recvtclass and recvttl, or for a single send operation the option(s) to override the currently active socket option(s).
getifaddrs_ifopts() =
[Ifopt ::
{flags,
Flags ::
[up | broadcast | loopback | pointtopoint |
running | multicast]} |
{addr, Addr :: ip_address()} |
{netmask, Netmask :: ip_address()} |
{broadaddr, Broadaddr :: ip_address()} |
{dstaddr, Dstaddr :: ip_address()} |
{hwaddr, Hwaddr :: [byte()]}]
Interface address description list returned from getifaddrs/0,1 for a named interface, translated from the returned data of the POSIX API function getaddrinfo().
Hwaddr is hardware dependent, for example, on Ethernet interfaces it is the 6-byte Ethernet address (MAC address (EUI-48 address)).
The tuples {addr,Addr}, {netmask,Netmask}, and possibly {broadaddr,Broadaddr} or {dstaddr,Dstaddr} are repeated in the list if the interface has got multiple addresses. An interface may have multiple {flag,_} tuples for example if it has different flags for different address families. Multiple {hwaddr,Hwaddr} tuples is hard to say anything definite about, though. The tuple {flag,Flags} is mandatory, all others are optional.
Do not rely too much on the order of Flags atoms or the Ifopt tuples. There are however some rules:
The tuple {hwaddr,_} is not returned on Solaris, as the hardware address historically belongs to the link layer and it is not returned by the Solaris API function getaddrinfo().
posix() =
eaddrinuse | eaddrnotavail | eafnosupport | ealready |
econnaborted | econnrefused | econnreset | edestaddrreq |
ehostdown | ehostunreach | einprogress | eisconn | emsgsize |
enetdown | enetunreach | enopkg | enoprotoopt | enotconn |
enotty | enotsock | eproto | eprotonosupport | eprototype |
esocktnosupport | etimedout | ewouldblock | exbadport |
exbadseq |
file:posix()
An atom that is named from the POSIX error codes used in Unix, and in the runtime libraries of most C compilers. See section POSIX Error Codes.
socket()
See gen_tcp:type-socket and gen_udp:type-socket.
address_family() = inet | inet6 | local
socket_protocol() = tcp | udp | sctp
stat_option() =
recv_cnt | recv_max | recv_avg | recv_oct | recv_dvi |
send_cnt | send_max | send_avg | send_oct | send_pend
close(Socket) -> ok
Types:
Closes a socket of any type.
format_error(Reason) -> string()
Types:
Returns a diagnostic error string. For possible POSIX values and corresponding strings, see section POSIX Error Codes.
get_rc() ->
[{Par :: atom(), Val :: any()} |
{Par :: atom(), Val1 :: any(), Val2 :: any()}]
Returns the state of the Inet configuration database in form of a list of recorded configuration parameters. For more information, see ERTS User's Guide: Inet Configuration.
Only actual parameters with other than default values are returned, for example not directives that specify other sources for configuration parameters nor directives that clear parameters.
getaddr(Host, Family) -> {ok, Address} | {error, posix()}
Types:
Returns the IP address for Host as a tuple of integers. Host can be an IP address, a single hostname, or a fully qualified hostname.
getaddrs(Host, Family) -> {ok, Addresses} | {error, posix()}
Types:
Returns a list of all IP addresses for Host. Host can be an IP address, a single hostname, or a fully qualified hostname.
gethostbyaddr(Address) -> {ok, Hostent} | {error, posix()}
Types:
Returns a hostent record for the host with the specified address.
gethostbyname(Hostname) -> {ok, Hostent} | {error, posix()}
Types:
Returns a hostent record for the host with the specified hostname.
If resolver option inet6 is true, an IPv6 address is looked up.
gethostbyname(Hostname, Family) ->
{ok, Hostent} | {error, posix()}
Types:
Returns a hostent record for the host with the specified name, restricted to the specified address family.
gethostname() -> {ok, Hostname}
Types:
Returns the local hostname. Never fails.
getifaddrs() ->
{ok,
[{Ifname :: string(),
Ifopts :: getifaddrs_ifopts()}]} |
{error, posix()}
Returns a list of 2-tuples containing interface names and the interfaces' addresses. Ifname is a Unicode string and Ifopts is a list of interface address description tuples.
The interface address description tuples are documented under the type of the Ifopts value.
getifaddrs(Opts) -> {ok, [{Ifname, Ifopts}]} | {error,
Posix}
Types:
The same as getifaddrs/0 but the Option {netns, Namespace} sets a network namespace for the OS call, on platforms that supports that feature.
See the socket option {netns, Namespace} under setopts/2.
getopts(Socket, Options) -> {ok, OptionValues} | {error, posix()}
Types:
Gets one or more options for a socket. For a list of available options, see setopts/2. See also the description for the type gen_tcp:pktoptions_value().
The number of elements in the returned OptionValues list does not necessarily correspond to the number of options asked for. If the operating system fails to support an option, it is left out in the returned list. An error tuple is returned only when getting options for the socket is impossible (that is, the socket is closed or the buffer size in a raw request is too large). This behavior is kept for backward compatibility reasons.
A raw option request RawOptReq = {raw, Protocol, OptionNum, ValueSpec} can be used to get information about socket options not (explicitly) supported by the emulator. The use of raw socket options makes the code non-portable, but allows the Erlang programmer to take advantage of unusual features present on a particular platform.
RawOptReq consists of tag raw followed by the protocol level, the option number, and either a binary or the size, in bytes, of the buffer in which the option value is to be stored. A binary is to be used when the underlying getsockopt requires input in the argument field. In this case, the binary size is to correspond to the required buffer size of the return value. The supplied values in a RawOptReq correspond to the second, third, and fourth/fifth parameters to the getsockopt call in the C socket API. The value stored in the buffer is returned as a binary ValueBin, where all values are coded in the native endianess.
Asking for and inspecting raw socket options require low-level information about the current operating system and TCP stack.
Example:
Consider a Linux machine where option TCP_INFO can be used to collect TCP statistics for a socket. Assume you are interested in field tcpi_sacked of struct tcp_info filled in when asking for TCP_INFO. To be able to access this information, you need to know the following:
By inspecting the headers or writing a small C program, it is found that IPPROTO_TCP is 6, TCP_INFO is 11, the structure size is 92 (bytes), the offset of tcpi_sacked is 28 bytes, and the value is a 32-bit integer. The following code can be used to retrieve the value:
get_tcpi_sacked(Sock) ->
{ok,[{raw,_,_,Info}]} = inet:getopts(Sock,[{raw,6,11,92}]),
<<_:28/binary,TcpiSacked:32/native,_/binary>> = Info,
TcpiSacked.
Preferably, you would check the machine type, the operating system, and the Kernel version before executing anything similar to this code.
getstat(Socket) -> {ok, OptionValues} | {error, posix()}
getstat(Socket, Options) -> {ok, OptionValues} | {error, posix()}
Types:
stat_option() =
recv_cnt | recv_max | recv_avg | recv_oct | recv_dvi |
send_cnt | send_max | send_avg | send_oct | send_pend
Gets one or more statistic options for a socket.
getstat(Socket) is equivalent to getstat(Socket, [recv_avg, recv_cnt, recv_dvi, recv_max, recv_oct, send_avg, send_cnt, send_pend, send_max, send_oct]).
The following options are available:
i() -> ok
i(Proto :: socket_protocol()) -> ok
i(X1 :: socket_protocol(), Fs :: [atom()]) -> ok
Lists all TCP, UDP and SCTP sockets, including those that the Erlang runtime system uses as well as those created by the application.
The following options are available:
ntoa(IpAddress) -> Address | {error, einval}
Types:
Parses an ip_address() and returns an IPv4 or IPv6 address string.
parse_address(Address) -> {ok, IPAddress} | {error, einval}
Types:
Parses an IPv4 or IPv6 address string and returns an ip4_address() or ip6_address(). Accepts a shortened IPv4 address string.
parse_ipv4_address(Address) -> {ok, IPv4Address} | {error, einval}
Types:
Parses an IPv4 address string and returns an ip4_address(). Accepts a shortened IPv4 address string.
parse_ipv4strict_address(Address) ->
{ok, IPv4Address} | {error, einval}
Types:
Parses an IPv4 address string containing four fields, that is, not shortened, and returns an ip4_address().
parse_ipv6_address(Address) -> {ok, IPv6Address} | {error, einval}
Types:
Parses an IPv6 address string and returns an ip6_address(). If an IPv4 address string is specified, an IPv4-mapped IPv6 address is returned.
parse_ipv6strict_address(Address) ->
{ok, IPv6Address} | {error, einval}
Types:
Parses an IPv6 address string and returns an ip6_address(). Does not accept IPv4 addresses.
ipv4_mapped_ipv6_address(X1 :: ip_address()) -> ip_address()
Convert an IPv4 address to an IPv4-mapped IPv6 address or the reverse. When converting from an IPv6 address all but the 2 low words are ignored so this function also works on some other types of addresses than IPv4-mapped.
parse_strict_address(Address) -> {ok, IPAddress} | {error, einval}
Types:
Parses an IPv4 or IPv6 address string and returns an ip4_address() or ip6_address(). Does not accept a shortened IPv4 address string.
peername(Socket :: socket()) ->
{ok,
{ip_address(), port_number()} |
returned_non_ip_address()} |
{error, posix()}
Returns the address and port for the other end of a connection.
Notice that for SCTP sockets, this function returns only one of the peer addresses of the socket. Function peernames/1,2 returns all.
peernames(Socket :: socket()) ->
{ok,
[{ip_address(), port_number()} |
returned_non_ip_address()]} |
{error, posix()}
Equivalent to peernames(Socket, 0).
Notice that the behavior of this function for an SCTP one-to-many style socket is not defined by the SCTP Sockets API Extensions.
peernames(Socket, Assoc) ->
{ok, [{Address, Port}]} | {error, posix()}
Types:
Returns a list of all address/port number pairs for the other end of an association Assoc of a socket.
This function can return multiple addresses for multihomed sockets, such as SCTP sockets. For other sockets it returns a one-element list.
Notice that parameter Assoc is by the SCTP Sockets API Extensions defined to be ignored for one-to-one style sockets. What the special value 0 means, hence its behavior for one-to-many style sockets, is unfortunately undefined.
port(Socket) -> {ok, Port} | {error, any()}
Types:
Returns the local port number for a socket.
setopts(Socket, Options) -> ok | {error, posix()}
Types:
Sets one or more options for a socket.
The following options are available:
If the value is false (passive mode), the process must explicitly receive incoming data by calling gen_tcp:recv/2,3, gen_udp:recv/2,3, or gen_sctp:recv/1,2 (depending on the type of socket).
If the value is once ({active, once}), one data message from the socket is sent to the process. To receive one more message, setopts/2 must be called again with option {active, once}.
If the value is an integer N in the range -32768 to 32767 (inclusive), the value is added to the socket's count of data messages sent to the controlling process. A socket's default message count is 0. If a negative value is specified, and its magnitude is equal to or greater than the socket's current message count, the socket's message count is set to 0. Once the socket's message count reaches 0, either because of sending received data messages to the process or by being explicitly set, the process is then notified by a special message, specific to the type of socket, that the socket has entered passive mode. Once the socket enters passive mode, to receive more messages setopts/2 must be called again to set the socket back into an active mode.
When using {active, once} or {active, N}, the socket changes behavior automatically when data is received. This can be confusing in combination with connection-oriented sockets (that is, gen_tcp), as a socket with {active, false} behavior reports closing differently than a socket with {active, true} behavior. To simplify programming, a socket where the peer closed, and this is detected while in {active, false} mode, still generates message {tcp_closed,Socket} when set to {active, once}, {active, true}, or {active, N} mode. It is therefore safe to assume that message {tcp_closed,Socket}, possibly followed by socket port termination (depending on option exit_on_close) eventually appears when a socket changes back and forth between {active, true} and {active, false} mode. However, when peer closing is detected it is all up to the underlying TCP/IP stack and protocol.
Notice that {active, true} mode provides no flow control; a fast sender can easily overflow the receiver with incoming messages. The same is true for {active, N} mode, while the message count is greater than zero.
Use active mode only if your high-level protocol provides its own flow control (for example, acknowledging received messages) or the amount of data exchanged is small. {active, false} mode, use of the {active, once} mode, or {active, N} mode with values of N appropriate for the application provides flow control. The other side cannot send faster than the receiver can read.
Note that this is also the maximum amount of data that can be received from a single recv call. If you are using higher than normal MTU consider setting buffer higher.
The only reason to set it to false is if you want to continue sending data to the socket after a close is detected, for example, if the peer uses gen_tcp:shutdown/2 to shut down the write side.
Senders of data to the socket are suspended if either the socket message queue is busy or the socket itself is busy.
For more information, see options low_msgq_watermark, high_watermark, and low_watermark.
Notice that distribution sockets disable the use of high_msgq_watermark and low_msgq_watermark. Instead use the distribution buffer busy limit, which is a similar feature.
Senders of data to the socket are suspended if either the socket message queue is busy or the socket itself is busy.
For more information, see options low_watermark, high_msgq_watermark, and low_msqg_watermark.
On most platforms this option must be set on the socket before associating it to an address. It is therefore only reasonable to specify it when creating the socket and not to use it when calling function (setopts/2) containing this description.
The behavior of a socket with this option set to true is the only portable one. The original idea when IPv6 was new of using IPv6 for all traffic is now not recommended by FreeBSD (you can use {ipv6_v6only,false} to override the recommended system default value), forbidden by OpenBSD (the supported GENERIC kernel), and impossible on Windows (which has separate IPv4 and IPv6 protocol stacks). Most Linux distros still have a system default value of false. This policy shift among operating systems to separate IPv6 from IPv4 traffic has evolved, as it gradually proved hard and complicated to get a dual stack implementation correct and secure.
On some platforms, the only allowed value for this option is true, for example, OpenBSD and Windows. Trying to set this option to false, when creating the socket, fails in this case.
Setting this option on platforms where it does not exist is ignored. Getting this option with getopts/2 returns no value, that is, the returned list does not contain an {ipv6_v6only,_} tuple. On Windows, the option does not exist, but it is emulated as a read-only option with value true.
Therefore, setting this option to true when creating a socket never fails, except possibly on a platform where you have customized the kernel to only allow false, which can be doable (but awkward) on, for example, OpenBSD.
If you read back the option value using getopts/2 and get no value, the option does not exist in the host operating system. The behavior of both an IPv6 and an IPv4 socket listening on the same port, and for an IPv6 socket getting IPv4 traffic is then no longer predictable.
The first component is if linger is enabled, the second component is the flushing time-out, in seconds. There are 3 alternatives:
This avoids TCP's TIME_WAIT state, but leaves open the possibility that another "incarnation" of this connection being created.
Senders that are suspended because of either a busy message queue or a busy socket are resumed when the socket message queue and the socket are not busy.
For more information, see options high_msgq_watermark, high_watermark, and low_watermark.
Notice that distribution sockets disable the use of high_msgq_watermark and low_msgq_watermark. Instead they use the distribution buffer busy limit, which is a similar feature.
Senders that are suspended because of a busy message queue or a busy socket are resumed when the socket message queue and the socket are not busy.
For more information, see options high_watermark, high_msgq_watermark, and low_msgq_watermark.
This option uses the Linux-specific syscall setns(), such as in Linux kernel 3.0 or later, and therefore only exists when the runtime system is compiled for such an operating system.
The virtual machine also needs elevated privileges, either running as superuser or (for Linux) having capability CAP_SYS_ADMIN according to the documentation for setns(2). However, during testing also CAP_SYS_PTRACE and CAP_DAC_READ_SEARCH have proven to be necessary.
Example:
setcap cap_sys_admin,cap_sys_ptrace,cap_dac_read_search+epi beam.smp
Notice that the filesystem containing the virtual machine executable (beam.smp in the example) must be local, mounted without flag nosetuid, support extended attributes, and the kernel must support file capabilities. All this runs out of the box on at least Ubuntu 12.04 LTS, except that SCTP sockets appear to not support network namespaces.
Namespace is a filename and is encoded and decoded as discussed in module file, with the following exceptions:
Unlike getifaddrs/0, Ifname is encoded a binary. In the unlikely case that a system is using non-7-bit-ASCII characters in network device names, special care has to be taken when encoding this argument.
This option uses the Linux-specific socket option SO_BINDTODEVICE, such as in Linux kernel 2.0.30 or later, and therefore only exists when the runtime system is compiled for such an operating system.
Before Linux 3.8, this socket option could be set, but could not retrieved with getopts/2. Since Linux 3.8, it is readable.
The virtual machine also needs elevated privileges, either running as superuser or (for Linux) having capability CAP_NET_RAW.
The primary use case for this option is to bind sockets into Linux VRF instances.
If Boolean == true, the corresponding option is turned on for the socket, which means that small amounts of data are accumulated until a full MSS-worth of data is available or this option is turned off.
Note that while TCP_NOPUSH socket option is available on OSX, its semantics is very different (e.g., unsetting it does not cause immediate send of accumulated data). Hence, nopush option is intentionally ignored on OSX.
The 4-byte header is limited to 2Gb.
The meanings of the packet types are as follows:
For line-oriented protocols (line, http*), option packet_size also guarantees that lines up to the indicated length are accepted and not considered invalid because of internal buffer limitations.
For packet oriented sockets that supports receiving ancillary data with the payload data (gen_udp and gen_sctp), the TCLASS value is returned in an extended return tuple contained in an ancillary data list. For stream oriented sockets (gen_tcp) the only way to get the TCLASS value is if the platform supports the pktoptions option.
For packet oriented sockets that supports receiving ancillary data with the payload data (gen_udp and gen_sctp), the TOS value is returned in an extended return tuple contained in an ancillary data list. For stream oriented sockets (gen_tcp) the only way to get the TOS value is if the platform supports the pktoptions option.
For packet oriented sockets that supports receiving ancillary data with the payload data (gen_udp and gen_sctp), the TTL value is returned in an extended return tuple contained in an ancillary data list. For stream oriented sockets (gen_tcp) the only way to get the TTL value is if the platform supports the pktoptions option.
Specifies a longest time to wait for a send operation to be accepted by the underlying TCP stack. When the limit is exceeded, the send operation returns {error,timeout}. How much of a packet that got sent is unknown; the socket is therefore to be closed whenever a time-out has occurred (see send_timeout_close below). Defaults to infinity.
Used together with send_timeout to specify whether the socket is to be automatically closed when the send operation returns {error,timeout}. The recommended setting is true, which automatically closes the socket. Defaults to false because of backward compatibility.
Setting this option to true allows you to distinguish between a connection that was closed normally, and one that was aborted (intentionally or unintentionally) by the TCP peer. A call to gen_tcp:recv/2 returns {error, econnreset}. In active mode, the controlling process receives a {tcp_error, Socket, econnreset} message before the usual {tcp_closed, Socket}, as is the case for any other socket error. Calls to gen_tcp:send/2 also returns {error, econnreset} when it is detected that a TCP peer has sent an RST.
A connected socket returned from gen_tcp:accept/1 inherits the show_econnreset setting from the listening socket.
In addition to these options, raw option specifications can be used. The raw options are specified as a tuple of arity four, beginning with tag raw, followed by the protocol level, the option number, and the option value specified as a binary. This corresponds to the second, third, and fourth arguments to the setsockopt call in the C socket API. The option value must be coded in the native endianess of the platform and, if a structure is required, must follow the structure alignment conventions on the specific platform.
Using raw socket options requires detailed knowledge about the current operating system and TCP stack.
Example:
This example concerns the use of raw options. Consider a Linux system where you want to set option TCP_LINGER2 on protocol level IPPROTO_TCP in the stack. You know that on this particular system it defaults to 60 (seconds), but you want to lower it to 30 for a particular socket. Option TCP_LINGER2 is not explicitly supported by inet, but you know that the protocol level translates to number 6, the option number to number 8, and the value is to be specified as a 32-bit integer. You can use this code line to set the option for the socket named Sock:
inet:setopts(Sock,[{raw,6,8,<<30:32/native>>}]),
As many options are silently discarded by the stack if they are specified out of range; it can be a good idea to check that a raw option is accepted. The following code places the value in variable TcpLinger2:
{ok,[{raw,6,8,<<TcpLinger2:32/native>>}]}=inet:getopts(Sock,[{raw,6,8,4}]),
Code such as these examples is inherently non-portable, even different versions of the same OS on the same platform can respond differently to this kind of option manipulation. Use with care.
Notice that the default options for TCP/IP sockets can be changed with the Kernel configuration parameters mentioned in the beginning of this manual page.
sockname(Socket :: socket()) ->
{ok,
{ip_address(), port_number()} |
returned_non_ip_address()} |
{error, posix()}
Returns the local address and port number for a socket.
Notice that for SCTP sockets this function returns only one of the socket addresses. Function socknames/1,2 returns all.
socknames(Socket :: socket()) ->
{ok,
[{ip_address(), port_number()} |
returned_non_ip_address()]} |
{error, posix()}
Equivalent to socknames(Socket, 0).
socknames(Socket, Assoc) ->
{ok, [{Address, Port}]} | {error, posix()}
Types:
Returns a list of all local address/port number pairs for a socket for the specified association Assoc.
This function can return multiple addresses for multihomed sockets, such as SCTP sockets. For other sockets it returns a one-element list.
Notice that parameter Assoc is by the SCTP Sockets API Extensions defined to be ignored for one-to-one style sockets. For one-to-many style sockets, the special value 0 is defined to mean that the returned addresses must be without any particular association. How different SCTP implementations interpret this varies somewhat.
| kernel 7.2 | Ericsson AB |