ranch/manual/ranch_transport.md

ranch_transport

The ranch_transport behaviour defines the interface used by Ranch transports.

Types

sendfile_opts() = [{chunk_size, non_neg_integer()}]

Options used by the sendfile function and callbacks.

Allows configuring the chunk size, in bytes. Defaults to 8191 bytes.

Callbacks

accept(LSocket, Timeout)

-> {ok, CSocket} | {error, closed | timeout | atom()}

Types:

• LSocket = CSocket = any()
• Timeout = timeout()

Accept a connection on the given listening socket.

The accept_ack callback will be used to initialize the socket after accepting the connection. This is most useful when the transport is not raw TCP, like with SSL for example.

accept_ack(CSocket, Timeout) -> ok

Types:

• CSocket = any()
• Timeout = timeout()

Perform post-accept initialization of the connection.

This function will be called by connection processes before performing any socket operation. It allows transports that require extra initialization to perform their task and make the socket ready to use.

close(CSocket) -> ok

Types:

• CSocket = any()

Close the given socket.

controlling_process(CSocket, Pid)

-> ok | {error, closed | not_owner | atom()}

Types:

• CSocket = any()
• Pid = pid()

Change the controlling process for the given socket.

The controlling process is the process that is allowed to perform operations on the socket, and that will receive messages from the socket when active mode is used. When the controlling process dies, the socket is closed.

listen(TransOpts) -> {ok, LSocket} | {error, atom()}

Types:

• TransOpts = any()
• LSocket = any()

Listen for connections on the given port.

The port is given as part of the transport options under the key port. Any other option is transport dependent.

The socket returned by this call can then be used to accept connections. It is not possible to send or receive data from the listening socket.

messages() -> {OK, Closed, Error}

Types:

• OK = Closed = Error = atom()

Return the atoms used to identify messages sent in active mode.

name() -> Name

Types:

• Name = atom()

Return the name of the transport.

peername(CSocket) -> {ok, {IP, Port}} | {error, atom()}

Types:

• CSocket = any()
• IP = inet:ip_address()
• Port = inet:port_number()

Return the IP and port of the remote endpoint.

recv(CSocket, Length, Timeout)

-> {ok, Packet} | {error, closed | timeout | atom()}

Types:

• CSocket = any()
• Length = non_neg_integer()
• Timeout = timeout()
• Packet = iodata() | any()

Receive data from the given socket when in passive mode.

Trying to receive data from a socket that is in active mode will return an error.

A length of 0 will return any data available on the socket.

While it is possible to use the timeout value infinity, this is highly discouraged as this could cause your process to get stuck waiting for data that will never come. This may happen when a socket becomes half-open due to a crash of the remote endpoint. Wi-Fi going down is another common culprit of this issue.

send(CSocket, Packet) -> ok | {error, atom()}

Types:

• CSocket = any()
• Packet = iodata()

Send data to the given socket.

sendfile(CSocket, File)

-> sendfile(CSocket, File, 0, 0, [])

sendfile(CSocket, File, Offset, Bytes)

-> sendfile(CSocket, File, Offset, Bytes, [])

sendfile(CSocket, File, Offset, Bytes, SfOpts)

-> {ok, SentBytes} | {error, atom()}

Types:

• CSocket = any()
• File = file:filename_all() | file:fd()
• Offset = non_neg_integer()
• Bytes = SentBytes = non_neg_integer()
• SfOpts = sendfile_opts()

Send data from a file to the given socket.

The file may be sent full or in parts, and may be specified by its filename or by an already open file descriptor.

Transports that manipulate TCP directly may use the file:sendfile/{2,4,5} function, which calls the sendfile syscall where applicable (on Linux, for example). Other transports can use the sendfile/6 function exported from this module.

setopts(CSocket, TransOpts) -> ok | {error, atom()}

Types:

• CSocket = any()
• TransOpts = any()

Change transport options for the given socket.

This is mainly useful for switching to active or passive mode.

sockname(CSocket) -> {ok, {IP, Port}} | {error, atom()}

Types:

• CSocket = any()
• IP = inet:ip_address()
• Port = inet:port_number()

Return the IP and port of the local endpoint.

Exports

sendfile(Transport, CSocket, File, Offset, Bytes, SfOpts)

-> {ok, SentBytes} | {error, atom()}

Types:

• Transport = module()
• CSocket = any()
• File = file:filename_all() | file:fd()
• Offset = non_neg_integer()
• Bytes = SentBytes = non_neg_integer()
• SfOpts = sendfile_opts()

Send data from a file to the given socket.

This function emulates the function file:sendfile/{2,4,5} and may be used when transports are not manipulating TCP directly.