"Fabian Cenedese" <[email protected]> wrote:
I'm trying to use socket and UDP (DGRAM) to receive data
from other devices.
addr.sin_len=sizeof(addr);
addr.sin_family=AF_INET;
addr.sin_port=PP_HTONS(MyPort);
addr.sin_addr.s_addr=PP_HTONL(INADDR_ANY);
s=socket(AF_INET, SOCK_DGRAM, 0);
ret=connect(s, (struct sockaddr*)&addr, sizeof(addr));
ret=read(s, buffer, size);
The calls are all successful, read is waiting. I can see the udp frame coming
in with the right port. However the frame is discarded in udp_input:
You'll have to add a call to bind(). Something like:
if (bind(sockfd, (struct sockaddr*)&addr, sizeof(struct sockaddr)) == -1)
{
perror ("bind");
return (-1);
}
From "man bind":
The bind(2) function assigns an address addr to an unnamed socket s. When
a socket is created with socket(2) it exists in a name space (address
family) but has no name assigned. The bind(2) function requests that name
be assigned to the socket.
When you don't call bind(), the socket remains "unnamed" (in BSD-lingo).
Hence, in lwIP lingo, the socket has "no recv function registered". Makes sense?
BTW. It's smarter to clear 'addr' before settting up the rest of it:
memset (&addr, 0, sizeof(addr));
--gv
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