errno 107 (ENOTCONN): meaning and diagnosis

Status / error code:		Category:

Constant name:
Source:		Operating System:
Description: an operation requires a connected socket but no peer connection is currently established.

Could be also:
Constant	Type	OS
ERROR_DISK_CHANGE	Win32 error	Windows
ECONNREFUSED	errno	Windows
PROCESS1_INITIALIZATION_FAILED	BugCheck Code	Windows

Previous	Next
EISCONN	ESHUTDOWN

ENOTCONN

ENOTCONN means the current socket has no established peer relationship required by the operation. A stream socket may never have completed connect(), may have been accepted incorrectly, or may already have been closed or shut down. For datagram sockets, it often means the program used a send-style call without a default peer and without supplying a destination.

The correct recovery depends on the socket type and call. A stream client normally creates a new socket and establishes a new connection; continuing on the same failed connection object is unsafe. A datagram client can either use sendto() with an address for each datagram or set a default peer with connect(). That datagram connect() is local socket configuration, not a TCP-style session handshake.

Do not confuse it with

EDESTADDRREQ: a datagram send has no destination address.
EISCONN: code is trying to connect or provide a destination when the socket is already connected.
EPIPE: a connection-oriented write hit a closed or shut-down path; Linux can report it in situations where another system might use ENOTCONN.

Linux recv(2) · Linux send(2) · GNU C Library error codes

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