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What does Recvfrom return in C++?

What does Recvfrom return in C++?

Return value If no error occurs, recvfrom returns the number of bytes received. If the connection has been gracefully closed, the return value is zero.

What is the use of socket Recvfrom ()?

The recvfrom() function shall receive 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. Specifies the socket file descriptor.

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.

Is recvFrom a blocking call?

If data is not available for the socket socket, and socket is in blocking mode, the recvfrom() call blocks the caller until data arrives.

Why is Recvfrom blocking?

By default, Recvfrom() is blocking: when a process issues a Recvfrom() that cannot be completed immediately (because there is no packet), the process is put to sleep waiting for a packet to arrive at the socket. Therefore, a call to Recvfrom() will return immediately only if a packet is available on the socket.

What does recv () return?

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.

Why would RECV fail?

If the connection has been reset, a recv will fail with the error WSAECONNRESET. The flags parameter can be used to influence the behavior of the function invocation beyond the options specified for the associated socket. The semantics of this function are determined by the socket options and the flags parameter.

How do I stop recvFrom?

Thread off your recvFrom() loop so that your main thread can wait for user input. When user requests stop, close the fd from the main thread and the recvFrom() will return immediately with an error, so allowing your recvFrom() thread to exit.

What is recv () in TCP?

The recv function is used to read incoming data on connection-oriented sockets, or connectionless sockets. When using a connection-oriented protocol, the sockets must be connected before calling recv. When using a connectionless protocol, the sockets must be bound before calling recv.

How does recvfrom work in C++?

The recvfrom function receives a datagram and stores the source address. A descriptor identifying a bound socket. A buffer for the incoming data. The length, in bytes, of the buffer pointed to by the buf parameter.

What is recvfrom () in socket programming?

The recvfrom () function applies to any datagram socket, whether connected or unconnected. The socket descriptor. The pointer to the buffer that receives the data.

How to initialize a pointer to a variable in C?

int i = 3; // A pointer to variable i (or stores // address of i) int *ptr = &i // A reference (or alias) for i. int &ref = i; 1. Initialization: A pointer can be initialized in this way: int a = 10; int *p = &a OR int *p; p = &a we can declare and initialize pointer at same step or in multiple line.

What is the return value of recvfrom in UDP?

For UDP if the packet received contains no data (empty), the return value from the recvfrom function function is zero. If the from parameter is nonzero and the socket is not connection oriented, (type SOCK_DGRAM for example), the network address of the peer that sent the data is copied to the corresponding sockaddr structure.