`wasi:sockets`

interface dependency

A WASI API for TCP & UDP sockets and domain name lookup.

interface `tcp-create-socket` `wasi:sockets/tcp-create-socket@0.2.6` since 0.2.0

Types

use resource `network`since 0.2.0

from wasi:sockets/network@0.2.6

An opaque resource that represents access to (a subset of) the network. This enables context-based security for networking. There is no need for this to map 1:1 to a physical network interface.

use enum `error-code`since 0.2.0

from wasi:sockets/network@0.2.6

Error codes.

In theory, every API can return any error code. In practice, API's typically only return the errors documented per API combined with a couple of errors that are always possible:

unknown
access-denied
not-supported
out-of-memory
concurrency-conflict

See each individual API for what the POSIX equivalents are. They sometimes differ per API.

unknown
Unknown error
access-denied
Access denied.

POSIX equivalent: EACCES, EPERM
not-supported
The operation is not supported.

POSIX equivalent: EOPNOTSUPP
invalid-argument
One of the arguments is invalid.

POSIX equivalent: EINVAL
out-of-memory
Not enough memory to complete the operation.

POSIX equivalent: ENOMEM, ENOBUFS, EAI_MEMORY
timeout
The operation timed out before it could finish completely.
concurrency-conflict
This operation is incompatible with another asynchronous operation that is already in progress.

POSIX equivalent: EALREADY
not-in-progress
Trying to finish an asynchronous operation that:
- has not been started yet, or:
- was already finished by a previous finish-* call.
Note: this is scheduled to be removed when futures are natively supported.
would-block
The operation has been aborted because it could not be completed immediately.

Note: this is scheduled to be removed when futures are natively supported.
invalid-state
The operation is not valid in the socket's current state.
new-socket-limit
A new socket resource could not be created because of a system limit.
address-not-bindable
A bind operation failed because the provided address is not an address that the network can bind to.
address-in-use
A bind operation failed because the provided address is already in use or because there are no ephemeral ports available.
remote-unreachable
The remote address is not reachable
connection-refused
The TCP connection was forcefully rejected
connection-reset
The TCP connection was reset.
connection-aborted
A TCP connection was aborted.
datagram-too-large
The size of a datagram sent to a UDP socket exceeded the maximum supported size.
name-unresolvable
Name does not exist or has no suitable associated IP addresses.
temporary-resolver-failure
A temporary failure in name resolution occurred.
permanent-resolver-failure
A permanent failure in name resolution occurred.

use enum `ip-address-family`since 0.2.0

from wasi:sockets/network@0.2.6

ipv4
Similar to AF_INET in POSIX.
ipv6
Similar to AF_INET6 in POSIX.

use resource `tcp-socket`since 0.2.0

from wasi:sockets/tcp@0.2.6

A TCP socket resource.

The socket can be in one of the following states:

unbound
bind-in-progress
bound (See note below)
listen-in-progress
listening
connect-in-progress
connected
closed See https://github.com/WebAssembly/wasi-sockets/blob/main/TcpSocketOperationalSemantics.md for more information.

Note: Except where explicitly mentioned, whenever this documentation uses the term "bound" without backticks it actually means: in the bound state or higher. (i.e. bound, listen-in-progress, listening, connect-in-progress or connected)

In addition to the general error codes documented on the network::error-code type, TCP socket methods may always return error(invalid-state) when in the closed state.

functionstart-bind: func( network: borrow<network>, local-address: ip-socket-address, ) -> result<_, error-code>since 0.2.0
Bind the socket to a specific network on the provided IP address and port.

If the IP address is zero (0.0.0.0 in IPv4, :: in IPv6), it is left to the implementation to decide which network interface(s) to bind to. If the TCP/UDP port is zero, the socket will be bound to a random free port.

Bind can be attempted multiple times on the same socket, even with different arguments on each iteration. But never concurrently and only as long as the previous bind failed. Once a bind succeeds, the binding can't be changed anymore.

Typical errors
- invalid-argument: The local-address has the wrong address family. (EAFNOSUPPORT, EFAULT on Windows)
- invalid-argument: local-address is not a unicast address. (EINVAL)
- invalid-argument: local-address is an IPv4-mapped IPv6 address. (EINVAL)
- invalid-state: The socket is already bound. (EINVAL)
- address-in-use: No ephemeral ports available. (EADDRINUSE, ENOBUFS on Windows)
- address-in-use: Address is already in use. (EADDRINUSE)
- address-not-bindable: local-address is not an address that the network can bind to. (EADDRNOTAVAIL)
- not-in-progress: A bind operation is not in progress.
- would-block: Can't finish the operation, it is still in progress. (EWOULDBLOCK, EAGAIN)
Implementors note

When binding to a non-zero port, this bind operation shouldn't be affected by the TIME_WAIT state of a recently closed socket on the same local address. In practice this means that the SO_REUSEADDR socket option should be set implicitly on all platforms, except on Windows where this is the default behavior and SO_REUSEADDR performs something different entirely.

Unlike in POSIX, in WASI the bind operation is async. This enables interactive WASI hosts to inject permission prompts. Runtimes that don't want to make use of this ability can simply call the native bind as part of either start-bind or finish-bind.

References
functionfinish-bind: func() -> result<_, error-code>since 0.2.0
functionstart-connect: func( network: borrow<network>, remote-address: ip-socket-address, ) -> result<_, error-code>since 0.2.0
Connect to a remote endpoint.

On success:
- the socket is transitioned into the connected state.
- a pair of streams is returned that can be used to read & write to the connection
After a failed connection attempt, the socket will be in the closed state and the only valid action left is to drop the socket. A single socket can not be used to connect more than once.

Typical errors
- invalid-argument: The remote-address has the wrong address family. (EAFNOSUPPORT)
- invalid-argument: remote-address is not a unicast address. (EINVAL, ENETUNREACH on Linux, EAFNOSUPPORT on MacOS)
- invalid-argument: remote-address is an IPv4-mapped IPv6 address. (EINVAL, EADDRNOTAVAIL on Illumos)
- invalid-argument: The IP address in remote-address is set to INADDR_ANY (0.0.0.0 / ::). (EADDRNOTAVAIL on Windows)
- invalid-argument: The port in remote-address is set to 0. (EADDRNOTAVAIL on Windows)
- invalid-argument: The socket is already attached to a different network. The network passed to connect must be identical to the one passed to bind.
- invalid-state: The socket is already in the connected state. (EISCONN)
- invalid-state: The socket is already in the listening state. (EOPNOTSUPP, EINVAL on Windows)
- timeout: Connection timed out. (ETIMEDOUT)
- connection-refused: The connection was forcefully rejected. (ECONNREFUSED)
- connection-reset: The connection was reset. (ECONNRESET)
- connection-aborted: The connection was aborted. (ECONNABORTED)
- remote-unreachable: The remote address is not reachable. (EHOSTUNREACH, EHOSTDOWN, ENETUNREACH, ENETDOWN, ENONET)
- address-in-use: Tried to perform an implicit bind, but there were no ephemeral ports available. (EADDRINUSE, EADDRNOTAVAIL on Linux, EAGAIN on BSD)
- not-in-progress: A connect operation is not in progress.
- would-block: Can't finish the operation, it is still in progress. (EWOULDBLOCK, EAGAIN)
Implementors note

The POSIX equivalent of start-connect is the regular connect syscall. Because all WASI sockets are non-blocking this is expected to return EINPROGRESS, which should be translated to ok() in WASI.

The POSIX equivalent of finish-connect is a poll for event POLLOUT with a timeout of 0 on the socket descriptor. Followed by a check for the SO_ERROR socket option, in case the poll signaled readiness.

References
functionfinish-connect: func() -> result<tuple<input-stream, output-stream>, error-code>since 0.2.0
functionstart-listen: func() -> result<_, error-code>since 0.2.0
Start listening for new connections.

Transitions the socket into the listening state.

Unlike POSIX, the socket must already be explicitly bound.

Typical errors
- invalid-state: The socket is not bound to any local address. (EDESTADDRREQ)
- invalid-state: The socket is already in the connected state. (EISCONN, EINVAL on BSD)
- invalid-state: The socket is already in the listening state.
- address-in-use: Tried to perform an implicit bind, but there were no ephemeral ports available. (EADDRINUSE)
- not-in-progress: A listen operation is not in progress.
- would-block: Can't finish the operation, it is still in progress. (EWOULDBLOCK, EAGAIN)
Implementors note

Unlike in POSIX, in WASI the listen operation is async. This enables interactive WASI hosts to inject permission prompts. Runtimes that don't want to make use of this ability can simply call the native listen as part of either start-listen or finish-listen.

References
functionfinish-listen: func() -> result<_, error-code>since 0.2.0
functionaccept: func() -> result<tuple<tcp-socket, input-stream, output-stream>, error-code>since 0.2.0
Accept a new client socket.

The returned socket is bound and in the connected state. The following properties are inherited from the listener socket:
- address-family
- keep-alive-enabled
- keep-alive-idle-time
- keep-alive-interval
- keep-alive-count
- hop-limit
- receive-buffer-size
- send-buffer-size
On success, this function returns the newly accepted client socket along with a pair of streams that can be used to read & write to the connection.

Typical errors
- invalid-state: Socket is not in the listening state. (EINVAL)
- would-block: No pending connections at the moment. (EWOULDBLOCK, EAGAIN)
- connection-aborted: An incoming connection was pending, but was terminated by the client before this listener could accept it. (ECONNABORTED)
- new-socket-limit: The new socket resource could not be created because of a system limit. (EMFILE, ENFILE)
References
functionlocal-address: func() -> result<ip-socket-address, error-code>since 0.2.0
Get the bound local address.

POSIX mentions:

If the socket has not been bound to a local name, the value stored in the object pointed to by address is unspecified.

WASI is stricter and requires local-address to return invalid-state when the socket hasn't been bound yet.

Typical errors
- invalid-state: The socket is not bound to any local address.
References
functionremote-address: func() -> result<ip-socket-address, error-code>since 0.2.0
Get the remote address.

Typical errors
- invalid-state: The socket is not connected to a remote address. (ENOTCONN)
References
functionis-listening: func() -> boolsince 0.2.0
Whether the socket is in the listening state.

Equivalent to the SO_ACCEPTCONN socket option.
functionaddress-family: func() -> ip-address-familysince 0.2.0
Whether this is a IPv4 or IPv6 socket.

Equivalent to the SO_DOMAIN socket option.
functionset-listen-backlog-size: func(value: u64) -> result<_, error-code>since 0.2.0
Hints the desired listen queue size. Implementations are free to ignore this.

If the provided value is 0, an invalid-argument error is returned. Any other value will never cause an error, but it might be silently clamped and/or rounded.

Typical errors
- not-supported: (set) The platform does not support changing the backlog size after the initial listen.
- invalid-argument: (set) The provided value was 0.
- invalid-state: (set) The socket is in the connect-in-progress or connected state.
functionkeep-alive-enabled: func() -> result<bool, error-code>since 0.2.0
Enables or disables keepalive.

The keepalive behavior can be adjusted using:
- keep-alive-idle-time
- keep-alive-interval
- keep-alive-count These properties can be configured while keep-alive-enabled is false, but only come into effect when keep-alive-enabled is true.
Equivalent to the SO_KEEPALIVE socket option.
functionset-keep-alive-enabled: func(value: bool) -> result<_, error-code>since 0.2.0
functionkeep-alive-idle-time: func() -> result<duration, error-code>since 0.2.0
Amount of time the connection has to be idle before TCP starts sending keepalive packets.

If the provided value is 0, an invalid-argument error is returned. Any other value will never cause an error, but it might be silently clamped and/or rounded. I.e. after setting a value, reading the same setting back may return a different value.

Equivalent to the TCP_KEEPIDLE socket option. (TCP_KEEPALIVE on MacOS)

Typical errors
- invalid-argument: (set) The provided value was 0.
functionset-keep-alive-idle-time: func(value: duration) -> result<_, error-code>since 0.2.0
functionkeep-alive-interval: func() -> result<duration, error-code>since 0.2.0
The time between keepalive packets.

If the provided value is 0, an invalid-argument error is returned. Any other value will never cause an error, but it might be silently clamped and/or rounded. I.e. after setting a value, reading the same setting back may return a different value.

Equivalent to the TCP_KEEPINTVL socket option.

Typical errors
- invalid-argument: (set) The provided value was 0.
functionset-keep-alive-interval: func(value: duration) -> result<_, error-code>since 0.2.0
functionkeep-alive-count: func() -> result<u32, error-code>since 0.2.0
The maximum amount of keepalive packets TCP should send before aborting the connection.

If the provided value is 0, an invalid-argument error is returned. Any other value will never cause an error, but it might be silently clamped and/or rounded. I.e. after setting a value, reading the same setting back may return a different value.

Equivalent to the TCP_KEEPCNT socket option.

Typical errors
- invalid-argument: (set) The provided value was 0.
functionset-keep-alive-count: func(value: u32) -> result<_, error-code>since 0.2.0
functionhop-limit: func() -> result<u8, error-code>since 0.2.0
Equivalent to the IP_TTL & IPV6_UNICAST_HOPS socket options.

If the provided value is 0, an invalid-argument error is returned.

Typical errors
- invalid-argument: (set) The TTL value must be 1 or higher.
functionset-hop-limit: func(value: u8) -> result<_, error-code>since 0.2.0
functionreceive-buffer-size: func() -> result<u64, error-code>since 0.2.0
The kernel buffer space reserved for sends/receives on this socket.

If the provided value is 0, an invalid-argument error is returned. Any other value will never cause an error, but it might be silently clamped and/or rounded. I.e. after setting a value, reading the same setting back may return a different value.

Equivalent to the SO_RCVBUF and SO_SNDBUF socket options.

Typical errors
- invalid-argument: (set) The provided value was 0.
functionset-receive-buffer-size: func(value: u64) -> result<_, error-code>since 0.2.0
functionsend-buffer-size: func() -> result<u64, error-code>since 0.2.0
functionset-send-buffer-size: func(value: u64) -> result<_, error-code>since 0.2.0
functionsubscribe: func() -> pollablesince 0.2.0
Create a pollable which can be used to poll for, or block on, completion of any of the asynchronous operations of this socket.

When finish-bind, finish-listen, finish-connect or accept return error(would-block), this pollable can be used to wait for their success or failure, after which the method can be retried.

The pollable is not limited to the async operation that happens to be in progress at the time of calling subscribe (if any). Theoretically, subscribe only has to be called once per socket and can then be (re)used for the remainder of the socket's lifetime.

See https://github.com/WebAssembly/wasi-sockets/blob/main/TcpSocketOperationalSemantics.md#pollable-readiness for more information.

Note: this function is here for WASI 0.2 only. It's planned to be removed when future is natively supported in Preview3.
functionshutdown: func(shutdown-type: shutdown-type) -> result<_, error-code>since 0.2.0
Initiate a graceful shutdown.
- receive: The socket is not expecting to receive any data from the peer. The input-stream associated with this socket will be closed. Any data still in the receive queue at time of calling this method will be discarded.
- send: The socket has no more data to send to the peer. The output-stream associated with this socket will be closed and a FIN packet will be sent.
- both: Same effect as receive & send combined.
This function is idempotent; shutting down a direction more than once has no effect and returns ok.

The shutdown function does not close (drop) the socket.

Typical errors
- invalid-state: The socket is not in the connected state. (ENOTCONN)
References

Functions

function`create-tcp-socket: func( address-family: ip-address-family, ) -> result<tcp-socket, error-code>`since 0.2.0

Create a new TCP socket.

Similar to socket(AF_INET or AF_INET6, SOCK_STREAM, IPPROTO_TCP) in POSIX. On IPv6 sockets, IPV6_V6ONLY is enabled by default and can't be configured otherwise.

This function does not require a network capability handle. This is considered to be safe because at time of creation, the socket is not bound to any network yet. Up to the moment bind/connect is called, the socket is effectively an in-memory configuration object, unable to communicate with the outside world.

All sockets are non-blocking. Use the wasi-poll interface to block on asynchronous operations.

Typical errors

not-supported: The specified address-family is not supported. (EAFNOSUPPORT)
new-socket-limit: The new socket resource could not be created because of a system limit. (EMFILE, ENFILE)

References

WIT

@since(version = 0.2.0)
interface tcp-create-socket {
  @since(version = 0.2.0)
  use network.{network, error-code, ip-address-family};
  @since(version = 0.2.0)
  use tcp.{tcp-socket};

  /// Create a new TCP socket.
  ///
  /// Similar to `socket(AF_INET or AF_INET6, SOCK_STREAM, IPPROTO_TCP)` in POSIX.
  /// On IPv6 sockets, IPV6_V6ONLY is enabled by default and can't be configured otherwise.
  ///
  /// This function does not require a network capability handle. This is considered to be safe because
  /// at time of creation, the socket is not bound to any `network` yet. Up to the moment `bind`/`connect`
  /// is called, the socket is effectively an in-memory configuration object, unable to communicate with the outside world.
  ///
  /// All sockets are non-blocking. Use the wasi-poll interface to block on asynchronous operations.
  ///
  /// # Typical errors
  /// - `not-supported`:     The specified `address-family` is not supported. (EAFNOSUPPORT)
  /// - `new-socket-limit`:  The new socket resource could not be created because of a system limit. (EMFILE, ENFILE)
  ///
  /// # References
  /// - <https://pubs.opengroup.org/onlinepubs/9699919799/functions/socket.html>
  /// - <https://man7.org/linux/man-pages/man2/socket.2.html>
  /// - <https://learn.microsoft.com/en-us/windows/win32/api/winsock2/nf-winsock2-wsasocketw>
  /// - <https://man.freebsd.org/cgi/man.cgi?query=socket&sektion=2>
  @since(version = 0.2.0)
  create-tcp-socket: func(address-family: ip-address-family) -> result<tcp-socket, error-code>;
}

wasi:sockets

interface tcp-create-socket wasi:sockets/tcp-create-socket@0.2.6 since 0.2.0

Types

use resource networksince 0.2.0

use enum error-codesince 0.2.0

use enum ip-address-familysince 0.2.0

use resource tcp-socketsince 0.2.0

Typical errors

Implementors note

References

Typical errors

Implementors note

References

Typical errors

Implementors note

References

Typical errors

References

Typical errors

References

Typical errors

References

Typical errors

Typical errors

Typical errors

Typical errors

Typical errors

Typical errors

Typical errors

References

Functions

functioncreate-tcp-socket: func( address-family: ip-address-family, ) -> result<tcp-socket, error-code>since 0.2.0

Typical errors

References

WIT

`wasi:sockets`

interface `tcp-create-socket` `wasi:sockets/tcp-create-socket@0.2.6` since 0.2.0

use resource `network`since 0.2.0

use enum `error-code`since 0.2.0

use enum `ip-address-family`since 0.2.0

use resource `tcp-socket`since 0.2.0

function`create-tcp-socket: func( address-family: ip-address-family, ) -> result<tcp-socket, error-code>`since 0.2.0