Kernel

User's Guide

Version 7.0

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• Reference Manual
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Chapters

• Introduction
  • Top of chapter
  • Scope
  • Prerequisites
• Socket Usage
  • Top of chapter
  • Introduction
  • Socket Options
• Logging
  • Top of chapter
  • Overview
  • Logger API
  • Filters
  • Handlers
  • Formatters
  • Configuration
  • Backwards Compatibility with error_logger
  • Error Handling
  • Example: Add a handler to log info events to file
  • Example: Implement a handler
  • Protecting the Handler from Overload
  • Logger Proxy
  • See Also
• Logging Cookbook
  • Top of chapter
  • Get Logger information
  • Configure the Logger
  • Configure Logger formatter
  • Configuring handlers
  • Logging
  • Filters
• EEP-48: Documentation storage and format
  • Top of chapter
  • the "Docs" storage
  • the "Docs" format
  • See Also

2 Socket Usage

2.1  Introduction

The socket interface (module) is basically an "thin" layer on top of the OS socket interface. It is assumed that, unless you have special needs, gen_[tcp|udp|sctp] should be sufficent (when they become available).

Note that just because we have a documented and described option, it does not mean that the OS supports it. So its recommended that the user reads the platform specific documentation for the option used.

Asynchronous calls

Some functions allow for an asynchronous call (accept/2, connect/3, recv/3,4, recvfrom/3,4, recvmsg/2,3,5, send/3,4, sendmsg/3,4 and sendto/4,5). This is achieved by setting the Timeout argument to nowait. For instance, if calling the recv/3 function with Timeout set to nowait (i.e. recv(Sock, 0, nowait)) when there is actually nothing to read, it will return with {select, SelectInfo} (SelectInfo contains the SelectRef). When data eventually arrives a 'select message' will be sent to the caller:

{'$socket', socket(), select, SelectRef}

The caller can then make another call to the recv function and now expect data.

Note that all other users are locked out until the 'current user' has called the function (recv in this case). So either immediately call the function or cancel.

The user must also be prepared to receive an abort message:

{'$socket', socket(), abort, Info}

If the operation is aborted for whatever reason (e.g. if the socket is closed "by someone else"). The Info part contains the abort reason (in this case that the socket has been closed Info = {SelectRef, closed}).

The general form of the 'socket' message is:

{'$socket', Sock :: socket(), Tag :: atom(), Info :: term()}

Where the format of Info is a function of Tag:

The select_ref() is the same as was received in the SelectInfo.

2.2  Socket Options

Options for level otp:

Options for level socket:

Options for level ip:

Options for level ipv6:

Options for level tcp:

Options for level udp:

Options for level sctp: