recv - Receive messages from connected sockets
int options );
[Tru64 UNIX] The following definition of the recv() function
does not conform to current standards and is supported
only for backward compatibility (see standards(5)):
int options );
Interfaces documented on this reference page conform to
industry standards as follows:
recv(): XNS4.0, XNS5.0
Refer to the standards(5) reference page for more information
about industry standards and associated tags.
Specifies the socket descriptor. Points to a buffer where
the message should be placed. Specifies the size of the
buffer pointed to by the buffer parameter. Points to a
value controlling the message reception. The options
parameter is formed by logically ORing one or more of the
following values, defined in the sys/socket.h file: Peek
at incoming message. The data is treated as unread and the
next recv() function (or similar function) will still
return this data. Process out-of-band data. Requests
that the function block wait until the full amount of data
requested can be returned. The function may return a
smaller amount of data if a signal is caught, the connection
is terminated, or an error is pending for the socket.
The recv() function receives messages from a connected
socket. The recvfrom() and recvmsg() functions receive
messages from both connected and unconnected sockets; however,
they are usually used for unconnected sockets only.
The recv() function returns the length of the message. If
a message is too long to fit in the supplied buffer,
excess bytes may be truncated depending on the type of
socket that issued the message.
If no messages are available at the socket, the recv()
function waits for a message to arrive, unless the socket
is nonblocking. If a socket is nonblocking, errno is set
Use the select() function to determine when more data
[Tru64 UNIX] The recv() function is identical to the
recvfrom() function with a zero-valued address_len parameter,
and to the read() function if no options are used.
For that reason the recv() function is disabled when
4.4BSD behavior is enabled; that is, when the _SOCKADDR_LEN
compile-time option is defined.
Upon successful completion, the recv() function returns
the length of the message in bytes. If no messages are
available and the peer has closed the connection, the
recv() function returns a value of 0. Otherwise, the function
returns a value of -1 and sets errno to indicate the
If the recv() function fails, errno may be set to one of
the following values: The read() would cause the information
label of the process to float to an information level
that is not dominated by the process's sensitivity level.
The socket parameter is not valid. A connection was
forcibly closed by a peer. The data was directed to be
received into a nonexistent or protected part of the process
address space. The buffer parameter is invalid. A
signal interrupted the recv() function before any data was
available. The MSG_OOB option is set and no out-of-band
data is available. An I/O error occurred while reading
from or writing to the file system. Insufficient
resources were available in the system to complete the
call. The system did not have sufficient memory to fulfill
the request. The available STREAMS resources were
insufficient for the operation to complete. Receive is
attempted on a connection-oriented socket that is not connected.
The socket parameter refers to a file, not a
socket. The specified options are not supported for this
socket type or protocol. The connection timed out during
connection establishment or due to a transmission timeout
on active connection. The socket is marked nonblocking,
and no data is waiting to be received.
Functions: recvfrom(2), recvmsg(2), send(2), sendmsg(2),
sendto(2), select(2), shutdown(2), socket(2), read(2),
Network Programmer's Guide
[ Back ]