Chapter 8, Interprocess communication using UNIX domain sockets
List of error codes

List of error codes

In the following is a list of networking error codes, the protocol or operation during which the error is likely to occur is given at the beginning of the explanation.

NOTE: If a connection fails at any time, the socket cannot be re-used; it must be closed and a new socket created.

I/O errors

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 EALREADY       Operation already in progress
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 EINPROGRESS    Operation now in progress
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 EWOULDBLOCK    Operation would block
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Argument errors

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 EADDRINUSE        Address already   An attempt was made
                   in use            to create a socket
                                     with a UNIX pathname
                                     which already
                                     exists.
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 EAFNOSUPPORT      Address family
                   not supported
                   by protocol
                   family
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 EDESTADDRREQ      Destination
                   address
                   required
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 EMSGSIZE          Message too
                   long
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 ENOTSOCK          Socket
                   operation on
                   non-socket
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 EOPNOTSUPP        Operation not
                   supported on
                   socket
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 EPFNOSUPPORT      Protocol family
                   not supported
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 EPROTONOSUPPORT   Protocol not      Creating a socket.
                   supported         Unknown protocol or
                                     protocol not
                                     supported.
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 EPROTOTYPE        Protocol wrong    Creating a socket.
                   type for socket   Socket type request
                                     has no supporting
                                     protocol.
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 ESOCKTNOSUPPORT   Socket type not
                   supported
 --------------------------------------------------------

Operational errors

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 ECONNABORTED   Software caused
                connection
                abort
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 ECONNREFUSED   Connection        Socket connection.
                refused           The host refused
                                  service for some
                                  reason.  This error
                                  is usually caused by
                                  a server process not
                                  being present at the
                                  requested name.
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 ECONNRESET     Connection        The remote peer
                reset by peer     forced the session
                                  to be closed.
 -----------------------------------------------------
 EISCONN        Socket is         An attempt was made
                already           to establish a
                connected         connection on a
                                  socket that already
                                  has one or an
                                  attempt was made to
                                  send a datagram with
                                  the destination
                                  address specified
                                  and the socket is
                                  already connected.
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 ENOBUFS        No buffer space   Any socket
                available         operation.  The
                                  system lacks
                                  sufficient memory
                                  for an internal data
                                  structure.
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 ENOENT         No such file or   Connection could not
                directory         be established.
 -----------------------------------------------------
 ENOTCONN       Socket is not     An attempt was made
                connected         to send a datagram,
                                  but no destination
                                  address is
                                  specified, and the
                                  socket has not been
                                  connected.
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 ESHUTDOWN      Cannot send
                after socket
                shutdown
 -----------------------------------------------------

Miscellaneous errors

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 ENOPROTOOPT    Protocol not
                available
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