|RECVFROM(3XNET)||X/Open Networking Services Library Functions||RECVFROM(3XNET)|
recvfrom - receive a message from a socket
cc [ flag ... ] file ... -lxnet [ library ... ] #include <sys/socket.h> ssize_t recvfrom(int socket, void *restrict buffer, size_t length,
int flags, struct sockaddr *restrict address,
socklen_t *restrict address_len);
The recvfrom() function receives a message from a connection-mode or connectionless-mode socket. It is normally used with connectionless-mode sockets because it permits the application to retrieve the source address of received data.
The function takes the following arguments:
The recvfrom() function returns the length of the message written to the buffer pointed to by the buffer argument. For message-based sockets such as SOCK_DGRAM and SOCK_SEQPACKET, the entire message must be read in a single operation. If a message is too long to fit in the supplied buffer, and MSG_PEEK is not set in the flags argument, the excess bytes are discarded. For stream-based sockets such as SOCK_STREAM, message boundaries are ignored. In this case, data is returned to the user as soon as it becomes available, and no data is discarded.
If the MSG_WAITALL flag is not set, data will be returned only up to the end of the first message.
Not all protocols provide the source address for messages. If the address argument is not a null pointer and the protocol provides the source address of messages, the source address of the received message is stored in the sockaddr structure pointed to by the address argument, and the length of this address is stored in the object pointed to by the address_len argument.
If the actual length of the address is greater than the length of the supplied sockaddr structure, the stored address will be truncated.
If the address argument is not a null pointer and the protocol does not provide the source address of messages, then the value stored in the object pointed to by address is unspecified.
If no messages are available at the socket and O_NONBLOCK is not set on the socket's file descriptor, recvfrom() blocks until a message arrives. If no messages are available at the socket and O_NONBLOCK is set on the socket's file descriptor, recvfrom() fails and sets errno to EAGAIN or EWOULDBLOCK.
Upon successful completion, recvfrom() returns the length of the message in bytes. If no messages are available to be received and the peer has performed an orderly shutdown, recvfrom() returns 0. Otherwise the function returns −1 and sets errno to indicate the error.
In addition to the errors documented below, an asynchronous error generated by the underlying socket protocol may be returned. For the full list of errors, please see the corresponding socket protocol manual page. For example, for a list of TCP errors, please see tcp(4P).
The recvfrom() function will fail if:
The recvfrom() function may fail if:
See attributes(7) for descriptions of the following attributes:
|ATTRIBUTE TYPE||ATTRIBUTE VALUE|
|September 10, 2018||OmniOS|