Non-blocking socket receive - c

Question

I have a simple server program that looks like the code below:
// create, bind, listen accept etc..
while(1)
{
UpdateData();
int ret = send(sock, data, dataLength , 0);
// Check if client sent "Abort" and if so, break.
}
Is it possible to check if any data has arrived from the client without blocking, so that the server can continuously dump data to the client?

Answer 1

Yes of course, there are a lot of solutions, AFAIK:
Thread
Non blocking mode
select()
poll()
epoll()
IOCP()
kqueue()
Not all available for all OS.

Answer 2

If your gonna define a non-blocking socket, you should add SOCK_NONBLOCK value in socket-type parameter when open a socket. for example this statement open a RAW socket in which can read and write TCP packets in non-blocking mode :
recv_socket = socket(AF_INET, SOCK_RAW | SOCK_NONBLOCK
, IPPROTO_TCP);
Then you can call read function as bellow :
typedef struct
{
struct iphdr ip;
struct tcphdr tcp;
char datagram[DATAGRAM_SIZE];
} TCP_PACKET;
int ret_read = 0;
TCP_PACKET recv_packet;
ret_read = read(recv_socket, reinterpret_cast<void*>(&received_packet)
, sizeof(received_packet));
if(ret_read >= 0)
{
// read occured in success
}
Notice : never use of const-size in read :
ret_read = read(recv_socket, reinterpret_cast<void*>(&received_packet)
, 65536); // makes segmentation fault
it makes segmentation fault while reading packets. just use of sizeof.