Is recv () a blocking call?
recv(IPC, Buffer, int n) is a blocking call, that is, if data is available it writes it to the buffer and immediately returns true, and if no data is available it waits for at least n seconds to receive any data.
What is the difference between read and recv?
The only difference between recv() and read(2) is the presence of flags. With a zero flags argument, recv() is generally equivalent to read(2) (but see NOTES).
Why does RECV return?
The recv() call applies only to connected sockets. This call returns the length of the incoming message or data. If a datagram packet is too long to fit in the supplied buffer, datagram sockets discard excess bytes.
What is recv error?
Return Value. Upon successful completion, recv() shall return the length of the message in bytes. If no messages are available to be received and the peer has performed an orderly shutdown, recv() shall return 0. Otherwise, -1 shall be returned and errno set to indicate the error.
Does recv wait for data?
If no messages are available at the socket, the recv() call waits for a message to arrive unless the socket is nonblocking. If a socket is nonblocking, -1 is returned and the external variable errno is set to EWOULDBLOCK. select() can be used to wait for incoming messages.
How does send and recv work?
After your connection is set up, the OS manages the packets entering and leaving your system, the recv() call just reads the packet buffer, and the send() call just queues the packets....Why is data received before recv() is called? ... The TCP stack takes care of sending/receiving the data.More items...•
How do I interrupt RECV?
To interrupt the thread, make the socket non-blocking (set O_NONBLOCK using fcntl ) and then signal the thread with pthread_kill . This way, recv will fail with either EINTR if it was sleeping, or EAGAIN or EWOULDBLOCK if it wasn't (also maybe if SA_RESTART is in effect, didn't check).
What is the difference between RECV and Recvfrom?
Unlike the recv() call, which can only be used on a connected stream socket or bound datagram socket, recvfrom() can be used to receive data on a socket whether or not it is connected. If no messages are available at the socket, the recvfrom() call waits for a message to arrive unless the socket is nonblocking.
What is a socket object?
A socket is an endpoint of communication—an object through which your application communicates with other Windows Sockets (Winsock) applications across a network. There are sockets on the client and server sides.
How do you make a non blocking recv?
In fact, if you reach a point where you actually WANT to wait for data on a socket that was previously marked as "non-blocking", you could simulate a blocking recv() just by calling select() first, followed by recv(). The "non-blocking" mode is set by changing one of the socket's "flags".
What is Msg_dontwait?
MSG_DONTWAIT (since Linux 2.2) Enables nonblocking operation; if the operation would block, EAGAIN or EWOULDBLOCK is returned.
What is the difference between RECV and Recvfrom?
Unlike the recv() call, which can only be used on a connected stream socket or bound datagram socket, recvfrom() can be used to receive data on a socket whether or not it is connected. If no messages are available at the socket, the recvfrom() call waits for a message to arrive unless the socket is nonblocking.
What is read return C?
The read() function reads data previously written to a file. If any portion of a regular file prior to the end-of-file has not been written, read() shall return bytes with value 0.
What is major difference between sent () and Sento () functions?
Generally speaking, send() is used for TCP SOCK_STREAM connected sockets, and sendto() is used for UDP SOCK_DGRAM unconnected datagram sockets.
What value of flag is kept in Recvfrom ()?
If successful, recvfrom() returns the length of the message or datagram in bytes. The value 0 indicates the connection is closed. If unsuccessful, recvfrom() returns -1 and sets errno to one of the following values: Error Code.