lwIP - A Minimal TCP/IP implementation - Wikia

18 CODE EXAMPLES
17.4.5 The recvfrom() and recvmsg() calls
The recvfrom() and recvmsg() calls are similar to the recv() call but differ in that the IP
address and port number of the sender of the data can be obtained through the call.
An implementation of recvmsg() is not included.
int
recvfrom(int s, void *mem, int len, unsigned int flags,
struct sockaddr *from, int *fromlen)
{
struct netconn *conn;
struct netbuf *buf;
struct ip_addr *addr;
unsigned short port;
int buflen;
}
conn = sockets[s];
buf = netconn_recv(conn);
buflen = netbuf_len(conn);
/* copy the contents of the received buffer into
the supplied memory pointer */
netbuf_copy(buf, mem, len);
addr = netbuf_fromaddr(buf);
port = netbuf_fromport(buf);
from->sin_addr = *addr;
from->sin_port = port;
*fromlen = sizeof(struct sockaddr);
netbuf_delete(buf);
/* if the length of the received data is larger than
len, this data is discarded and we return len.
otherwise we return the actual length of the received
data */
if(len > buflen) {
return buflen;
} else {
return len;
}
18 Code examples
18.1 Using the API
This section presents a simple web server written using the lwIP API. The application code is
given below. The application implements only the bare bones of an HTTP/1.0 [BLFF96] server
and is included only to show the principles in using the lwIP API for an actual application.
The application consists of a single process that accepts connections from the network, responds
to HTTP requests, and closes the connection. There are two functions in the application; main()
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