send/recv 와 write/read함수의 차이?
UNIX/Linux에서 모든 장치/자원은 FILE.
그래서 소켓이란 자원 역시 read/write라는 인터페이스로 입출력을 수행.
recv/send는 소켓 전용 인터페이스로 뒤에 옵션이 더 있음.
UNIX/Linux에선 아무거나 써도 무방하나,Windows에서 소켓은 recv/send만 사용가능
#include <sys/types.h>
#include <sys/socket.h>
#include <sys/uio.h>
ssize_t recv(int s, void *buf, size_t len, int flags);
ssize_t recvfrom(int s, void *buf, size_t len, int flags, struct sockaddr *from, socklen_t *fromlen);
ssize_t recvmsg(int s, struct msghdr *msg, int flags);
flags 값.
MSG_OOB
- Read any out-of-band data present on the socket rather than the regular in-band data.
MSG_PEEK
- Peek at the data present on the socket. The data is returned, but not consumed to allow a subsequent receive operation to see the same data.
MSG_WAITALL
- Messages are blocked until the full amount of data requested is returned. The recv() function can return a smaller amount of data if a signal is caught, the connection is terminated, MSG_PEEK is specified, or if an error is pending for the socket.
MSG_DONTWAIT
- Pending messages received on the connection are returned. If data is unavailable, the function does not block. This behavior is the equivalent to specifying O_NONBLOCK on the file descriptor of a socket, except that write requests are unaffected.
