Network.WebSockets

Incoming connections and handshaking

data PendingConnection

A new client connected to the server. We haven't accepted the connection yet, though.

pendingRequest :: PendingConnection -> RequestHead

Useful for e.g. inspecting the request path.

acceptRequest :: PendingConnection -> IO Connection

Accept a pending connection, turning it into a Connection.

data AcceptRequest

This datatype allows you to set options for acceptRequestWith. It is strongly recommended to use defaultAcceptRequest and then modify the various fields, that way new fields introduced in the library do not break your code.

Constructors

AcceptRequest

Fields

• acceptSubprotocol :: !(Maybe ByteString)

  The subprotocol to speak with the client. If pendingSubprotcols is non-empty, acceptSubprotocol must be one of the subprotocols from the list.

• acceptHeaders :: !Headers

  Extra headers to send with the response.

defaultAcceptRequest :: AcceptRequest

acceptRequestWith :: PendingConnection -> AcceptRequest -> IO Connection

This function is like acceptRequest but allows you to set custom options using the AcceptRequest datatype.

rejectRequest

Arguments

:: PendingConnection

Connection to reject

-> ByteString

Rejection response body

-> IO ()

data RejectRequest

Parameters that allow you to tweak how a request is rejected. Please use defaultRejectRequest and modify fields using record syntax so your code will not break when new fields are added.

Constructors

RejectRequest

Fields

• rejectCode :: !Int

  The status code, 400 by default.

• rejectMessage :: !ByteString

  The message, "Bad Request" by default

• rejectHeaders :: Headers

  Extra headers to be sent with the response.

• rejectBody :: !ByteString

  Reponse body of the rejection.

defaultRejectRequest :: RejectRequest

rejectRequestWith

Arguments

:: PendingConnection

Connection to reject

-> RejectRequest

Params on how to reject the request

-> IO ()

Main connection type

data Connection

Options for connections

data ConnectionOptions

Set options for a Connection. Please do not use this constructor directly, but rather use defaultConnectionOptions and then set the fields you want, e.g.:

myOptions = defaultConnectionOptions {connectionStrictUnicode = True}

This way your code does not break if the library introduces new fields.

Constructors

ConnectionOptions

Fields

• connectionOnPong :: !(IO ())

  Whenever a pong is received, this IO action is executed. It can be used to tickle connections or fire missiles.

• connectionCompressionOptions :: !CompressionOptions

  Enable PermessageDeflate.

• connectionStrictUnicode :: !Bool

  Enable strict unicode on the connection. This means that if a client (or server) sends invalid UTF-8, we will throw a UnicodeException rather than replacing it by the unicode replacement character U+FFFD.

• connectionFramePayloadSizeLimit :: !SizeLimit

  The maximum size for incoming frame payload size in bytes. If a frame exceeds this limit, a ParseException is thrown.

• connectionMessageDataSizeLimit :: !SizeLimit

  connectionFrameSizeLimit is often not enough since a malicious client can send many small frames to create a huge message. This limit allows you to protect from that. If a message exceeds this limit, a ParseException is thrown.

  Note that, if compression is enabled, we check the size of the compressed messages, as well as the size of the uncompressed messages as we are deflating them to ensure we don't use too much memory in any case.

defaultConnectionOptions :: ConnectionOptions

The default connection options:

• Nothing happens when a pong is received.
• Compression is disabled.
• Lenient unicode decoding.

Compression options

data CompressionOptions

Constructors

NoCompression

PermessageDeflateCompression PermessageDeflate

Instances

Eq CompressionOptions

Defined in Network.WebSockets.Connection.Options

Methods

(==) :: CompressionOptions -> CompressionOptions -> Bool

(/=) :: CompressionOptions -> CompressionOptions -> Bool

Show CompressionOptions

Defined in Network.WebSockets.Connection.Options

Methods

showsPrec :: Int -> CompressionOptions -> ShowS

show :: CompressionOptions -> String

showList :: [CompressionOptions] -> ShowS

data PermessageDeflate

Four extension parameters are defined for "permessage-deflate" to help endpoints manage per-connection resource usage.

• "server_no_context_takeover"
• "client_no_context_takeover"
• "server_max_window_bits"
• "client_max_window_bits"

Constructors

PermessageDeflate

Fields

• serverNoContextTakeover :: Bool
• clientNoContextTakeover :: Bool
• serverMaxWindowBits :: Int
• clientMaxWindowBits :: Int
• pdCompressionLevel :: Int

Instances

Eq PermessageDeflate

Defined in Network.WebSockets.Connection.Options

Methods

(==) :: PermessageDeflate -> PermessageDeflate -> Bool

(/=) :: PermessageDeflate -> PermessageDeflate -> Bool

Show PermessageDeflate

Defined in Network.WebSockets.Connection.Options

Methods

showsPrec :: Int -> PermessageDeflate -> ShowS

show :: PermessageDeflate -> String

showList :: [PermessageDeflate] -> ShowS

defaultPermessageDeflate :: PermessageDeflate

Protection limits

data SizeLimit

A size limit, in bytes. The Monoid instance takes the minimum limit.

Constructors

NoSizeLimit

SizeLimit !Int64

Instances

Eq SizeLimit

Defined in Network.WebSockets.Connection.Options

Methods

(==) :: SizeLimit -> SizeLimit -> Bool

(/=) :: SizeLimit -> SizeLimit -> Bool

Show SizeLimit

Defined in Network.WebSockets.Connection.Options

Methods

showsPrec :: Int -> SizeLimit -> ShowS

show :: SizeLimit -> String

showList :: [SizeLimit] -> ShowS

Semigroup SizeLimit

Defined in Network.WebSockets.Connection.Options

Methods

(<>) :: SizeLimit -> SizeLimit -> SizeLimit

sconcat :: NonEmpty SizeLimit -> SizeLimit

stimes :: Integral b => b -> SizeLimit -> SizeLimit

Monoid SizeLimit

Defined in Network.WebSockets.Connection.Options

Methods

mempty :: SizeLimit

mappend :: SizeLimit -> SizeLimit -> SizeLimit

mconcat :: [SizeLimit] -> SizeLimit

Sending and receiving messages

receive :: Connection -> IO Message

receiveDataMessage :: Connection -> IO DataMessage

Receive an application message. Automatically respond to control messages.

When the peer sends a close control message, an exception of type CloseRequest is thrown. The peer can send a close control message either to initiate a close or in response to a close message we have sent to the peer. In either case the CloseRequest exception will be thrown. The RFC specifies that the server is responsible for closing the TCP connection, which should happen after receiving the CloseRequest exception from this function.

This will throw ConnectionClosed if the TCP connection dies unexpectedly.

receiveData :: WebSocketsData a => Connection -> IO a

Receive a message, converting it to whatever format is needed.

send :: Connection -> Message -> IO ()

sendDataMessage :: Connection -> DataMessage -> IO ()

Send a Message. This allows you send both human-readable text and binary data. This is a slightly more low-level interface than sendTextData or sendBinaryData.

sendDataMessages :: Connection -> [DataMessage] -> IO ()

Send a collection of Messages. This is more efficient than calling sendDataMessage many times.

sendTextData :: WebSocketsData a => Connection -> a -> IO ()

Send a textual message. The message will be encoded as UTF-8. This should be the default choice for human-readable text-based protocols such as JSON.

sendTextDatas :: WebSocketsData a => Connection -> [a] -> IO ()

Send a number of textual messages. This is more efficient than calling sendTextData many times.

sendBinaryData :: WebSocketsData a => Connection -> a -> IO ()

Send a binary message. This is useful for sending binary blobs, e.g. images, data encoded with MessagePack, images...

sendBinaryDatas :: WebSocketsData a => Connection -> [a] -> IO ()

Send a number of binary messages. This is more efficient than calling sendBinaryData many times.

sendClose :: WebSocketsData a => Connection -> a -> IO ()

Send a friendly close message. Note that after sending this message, you should still continue calling receiveDataMessage to process any in-flight messages. The peer will eventually respond with a close control message of its own which will cause receiveDataMessage to throw the CloseRequest exception. This exception is when you can finally consider the connection closed.

sendCloseCode :: WebSocketsData a => Connection -> Word16 -> a -> IO ()

Send a friendly close message and close code. Similar to sendClose, you should continue calling receiveDataMessage until you receive a CloseRequest exception.

See http://tools.ietf.org/html/rfc6455#section-7.4 for a list of close codes.

sendPing :: WebSocketsData a => Connection -> a -> IO ()

Send a ping

HTTP Types

type Headers = [(CI ByteString, ByteString)]

Request headers

data Request

A request with a body

Constructors

Request RequestHead ByteString

Instances

Show Request

Defined in Network.WebSockets.Http

Methods

showsPrec :: Int -> Request -> ShowS

show :: Request -> String

showList :: [Request] -> ShowS

data RequestHead

An HTTP request. The request body is not yet read.

Constructors

RequestHead

Fields

• requestPath :: !ByteString
• requestHeaders :: Headers
• requestSecure :: Bool

Instances

Show RequestHead

Defined in Network.WebSockets.Http

Methods

showsPrec :: Int -> RequestHead -> ShowS

show :: RequestHead -> String

showList :: [RequestHead] -> ShowS

getRequestSubprotocols :: RequestHead -> [ByteString]

List of subprotocols specified by the client, in order of preference. If the client did not specify a list of subprotocols, this will be the empty list.

data Response

A response including a body

Constructors

Response ResponseHead ByteString

Instances

Show Response

Defined in Network.WebSockets.Http

Methods

showsPrec :: Int -> Response -> ShowS

show :: Response -> String

showList :: [Response] -> ShowS

data ResponseHead

HTTP response, without body.

Constructors

ResponseHead

Fields

• responseCode :: !Int
• responseMessage :: !ByteString
• responseHeaders :: Headers

Instances

Show ResponseHead

Defined in Network.WebSockets.Http

Methods

showsPrec :: Int -> ResponseHead -> ShowS

show :: ResponseHead -> String

showList :: [ResponseHead] -> ShowS

WebSocket message types

data Message

The kind of message a server application typically deals with

Constructors

ControlMessage ControlMessage

DataMessage Bool Bool Bool DataMessage

Reserved bits, actual message

Instances

Eq Message

Defined in Network.WebSockets.Types

Methods

(==) :: Message -> Message -> Bool

(/=) :: Message -> Message -> Bool

Show Message

Defined in Network.WebSockets.Types

Methods

showsPrec :: Int -> Message -> ShowS

show :: Message -> String

showList :: [Message] -> ShowS

data ControlMessage

Different control messages

Constructors

Close Word16 ByteString

Ping ByteString

Pong ByteString

Instances

Eq ControlMessage

Defined in Network.WebSockets.Types

Methods

(==) :: ControlMessage -> ControlMessage -> Bool

(/=) :: ControlMessage -> ControlMessage -> Bool

Show ControlMessage

Defined in Network.WebSockets.Types

Methods

showsPrec :: Int -> ControlMessage -> ShowS

show :: ControlMessage -> String

showList :: [ControlMessage] -> ShowS

data DataMessage

For an end-user of this library, dealing with Frames would be a bit low-level. This is why define another type on top of it, which represents data for the application layer.

There are currently two kinds of data messages supported by the WebSockets protocol:

• Textual UTF-8 encoded data. This corresponds roughly to sending a String in JavaScript.
• Binary data. This corresponds roughly to send an ArrayBuffer in JavaScript.

Constructors

Text ByteString (Maybe Text)

A textual message. The second field might contain the decoded UTF-8 text for caching reasons. This field is computed lazily so if it's not accessed, it should have no performance impact.

Binary ByteString

A binary message.

Instances

Eq DataMessage

Defined in Network.WebSockets.Types

Methods

(==) :: DataMessage -> DataMessage -> Bool

(/=) :: DataMessage -> DataMessage -> Bool

Show DataMessage

Defined in Network.WebSockets.Types

Methods

showsPrec :: Int -> DataMessage -> ShowS

show :: DataMessage -> String

showList :: [DataMessage] -> ShowS

class WebSocketsData a where

In order to have an even more high-level API, we define a typeclass for values the user can receive from and send to the socket. A few warnings apply:

• Natively, everything is represented as a ByteString, so this is the fastest instance
• You should only use the Text or the Text instance when you are sure that the data is UTF-8 encoded (which is the case for Text messages).
• Messages can be very large. If this is the case, it might be inefficient to use the strict ByteString and Text instances.

Methods

fromDataMessage :: DataMessage -> a

fromLazyByteString :: ByteString -> a

toLazyByteString :: a -> ByteString

Instances

WebSocketsData ByteString

Defined in Network.WebSockets.Types

Methods

fromDataMessage :: DataMessage -> ByteString

fromLazyByteString :: ByteString0 -> ByteString

toLazyByteString :: ByteString -> ByteString0

WebSocketsData ByteString

Defined in Network.WebSockets.Types

Methods

fromDataMessage :: DataMessage -> ByteString

fromLazyByteString :: ByteString -> ByteString

toLazyByteString :: ByteString -> ByteString

WebSocketsData Text

Defined in Network.WebSockets.Types

Methods

fromDataMessage :: DataMessage -> Text

fromLazyByteString :: ByteString -> Text

toLazyByteString :: Text -> ByteString

WebSocketsData Text

Defined in Network.WebSockets.Types

Methods

fromDataMessage :: DataMessage -> Text

fromLazyByteString :: ByteString -> Text

toLazyByteString :: Text -> ByteString

Exceptions

data HandshakeException

Error in case of failed handshake. Will be thrown as an Exception.

TODO: This should probably be in the Handshake module, and is solely here to prevent a cyclic dependency.

Constructors

NotSupported

We don't have a match for the protocol requested by the client. todo: version parameter

MalformedRequest RequestHead String

The request was somehow invalid (missing headers or wrong security token)

MalformedResponse ResponseHead String

The servers response was somehow invalid (missing headers or wrong security token)

RequestRejected Request String

The request was well-formed, but the library user rejected it. (e.g. "unknown path")

OtherHandshakeException String

for example "EOF came too early" (which is actually a parse error) or for your own errors. (like "unknown path"?)

Instances

Show HandshakeException

Defined in Network.WebSockets.Http

Methods

showsPrec :: Int -> HandshakeException -> ShowS

show :: HandshakeException -> String

showList :: [HandshakeException] -> ShowS

Exception HandshakeException

Defined in Network.WebSockets.Http

Methods

toException :: HandshakeException -> SomeException

fromException :: SomeException -> Maybe HandshakeException

displayException :: HandshakeException -> String

data ConnectionException

Various exceptions that can occur while receiving or transmitting messages

Constructors

CloseRequest Word16 ByteString

The peer has requested that the connection be closed, and included a close code and a reason for closing. When receiving this exception, no more messages can be sent. Also, the server is responsible for closing the TCP connection once this exception is received.

See http://tools.ietf.org/html/rfc6455#section-7.4 for a list of close codes.

ConnectionClosed

The peer unexpectedly closed the connection while we were trying to receive some data. This is a violation of the websocket RFC since the TCP connection should only be closed after sending and receiving close control messages.

ParseException String

The client sent garbage, i.e. we could not parse the WebSockets stream.

UnicodeException String

The client sent invalid UTF-8. Note that this exception will only be thrown if strict decoding is set in the connection options.

Instances

Eq ConnectionException

Defined in Network.WebSockets.Types

Methods

(==) :: ConnectionException -> ConnectionException -> Bool

(/=) :: ConnectionException -> ConnectionException -> Bool

Show ConnectionException

Defined in Network.WebSockets.Types

Methods

showsPrec :: Int -> ConnectionException -> ShowS

show :: ConnectionException -> String

showList :: [ConnectionException] -> ShowS

Exception ConnectionException

Defined in Network.WebSockets.Types

Methods

toException :: ConnectionException -> SomeException

fromException :: SomeException -> Maybe ConnectionException

displayException :: ConnectionException -> String

Running a standalone server

type ServerApp = PendingConnection -> IO ()

WebSockets application that can be ran by a server. Once this IO action finishes, the underlying socket is closed automatically.

runServer

Arguments

:: String

Address to bind

-> Int

Port to listen on

-> ServerApp

Application

-> IO ()

Never returns

Provides a simple server. This function blocks forever. Note that this is merely provided for quick-and-dirty or internal applications, but for real applications, you should use a real server.

For example:

• Performance is reasonable under load, but:
• No protection against DoS attacks is provided.
• No logging is performed.
• ...

Glue for using this package with real servers is provided by:

• https://hackage.haskell.org/package/wai-websockets
• https://hackage.haskell.org/package/websockets-snap

runServerWith :: String -> Int -> ConnectionOptions -> ServerApp -> IO ()

A version of runServer which allows you to customize some options.

Utilities for writing your own server

makeListenSocket :: String -> Int -> IO Socket

Create a standardized socket on which you can listen for incomming connections. Should only be used for a quick and dirty solution! Should be preceded by the call withSocketsDo.

makePendingConnection :: Socket -> ConnectionOptions -> IO PendingConnection

Turns a socket, connected to some client, into a PendingConnection. The PendingConnection should be closed using close later.

makePendingConnectionFromStream :: Stream -> ConnectionOptions -> IO PendingConnection

More general version of makePendingConnection for Stream instead of a Socket.

Running a client

type ClientApp a = Connection -> IO a

A client application interacting with a single server. Once this IO action finished, the underlying socket is closed automatically.

runClient

Arguments

:: String

Host

-> Int

Port

-> String

Path

-> ClientApp a

Client application

-> IO a

runClientWith

Arguments

:: String

Host

-> Int

Port

-> String

Path

-> ConnectionOptions

Options

-> Headers

Custom headers to send

-> ClientApp a

Client application

-> IO a

runClientWithSocket

Arguments

:: Socket

Socket

-> String

Host

-> String

Path

-> ConnectionOptions

Options

-> Headers

Custom headers to send

-> ClientApp a

Client application

-> IO a

runClientWithStream

Arguments

:: Stream

Stream

-> String

Host

-> String

Path

-> ConnectionOptions

Connection options

-> Headers

Custom headers to send

-> ClientApp a

Client application

-> IO a

newClientConnection

Arguments

:: Stream

Stream that will be used by the new Connection.

-> String

Host

-> String

Path

-> ConnectionOptions

Connection options

-> Headers

Custom headers to send

-> IO Connection

Build a new Connection from the client's point of view.

WARNING: Be sure to call close on the given Stream after you are done using the Connection in order to properly close the communication channel. runClientWithStream handles this for you, prefer to use it when possible.

Utilities

forkPingThread :: Connection -> Int -> IO ()

Forks a ping thread, sending a ping message every n seconds over the connection. The thread dies silently if the connection crashes or is closed.

This is useful to keep idle connections open through proxies and whatnot. Many (but not all) proxies have a 60 second default timeout, so based on that sending a ping every 30 seconds is a good idea.