Receives messages from connected sockets.
Standard C Library (libc.a)
The recv subroutine receives messages from a connected socket. The recvfrom and recvmsg subroutines receive messages from both connected and unconnected sockets. However, they are usually used for unconnected sockets only.
The recv subroutine 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 subroutine waits for a message to arrive, unless the socket is nonblocking. If a socket is nonblocking, the system returns an error.
Use the select subroutine to determine when more data arrives.
The socket applications can be compiled with COMPAT_43 defined. This will make the sockaddr structure BSD 4.3 compatible. For more details refer to socket.h.
Item | Description |
---|---|
Socket | Specifies the socket descriptor. |
Buffer | Specifies an address where the message should be placed. |
Length | Specifies the size of the Buffer parameter. |
Flags | Points to a value controlling the message reception. The
/usr/include/sys/socket.h file defines the Flags parameter.
The argument to receive a call is formed by logically ORing one or
more of the following values:
|
Upon successful completion, the recv subroutine returns the length of the message in bytes.
If the recv subroutine is unsuccessful, the subroutine handler performs the following functions:
The recv subroutine is unsuccessful if any of the following errors occurs:
Error | Description |
---|---|
EBADF | The Socket parameter is not valid. |
ECONNRESET | The remote peer forces the connection to be closed. |
EFAULT | The data was directed to be received into a nonexistent or protected part of the process address space. The Buffer parameter is not valid. |
EINTR | A signal interrupted the recv subroutine before any data was available. |
EINVAL | The MSG_OOB flag is set and no out-of-band data is available. |
ENOBUF | Insufficient resources are available in the system to perform the operation. |
ENOTCONN | A receive is attempted on a SOCK_STREAM socket that is not connected. |
ENOTSOCK | The Socket parameter refers to a file, not a socket. |
EOPNOTSUPP | MSG_OOB flag is set for a SOCK_DGRAM socket, or MSG_OOB flag is set for any AF_UNIX socket. |
ETIMEDOUT | The connection timed out during connection establishment, or there was a transmission timeout on an active connection. |
EWOULDBLOCK | The socket is marked nonblocking, and no connections are present to be accepted. |