Some Additional network API

• sendto, send, sendmsg
  • #include <sys/types.h>
  • #include <sys/socket.h>
  • send is for a connection, and the flags are the only difference from write
  • sendto can be on any type.
  • sendmsg uses a smghdr struct.
  • ssize_t sendto(int s, const void *buf, size_t len, int flags, const struct sockaddr *to, socklen_t tolen);
  • s is the socket
  • buf is the buffer containing the data to be sent
  • len is the length of the buffer
  • to is the information on where to send the msg, ignored in a tcp connection.
  • tolen is the length of the to field.
  • Flags (an or of these)
    • MSG_DONTROUTE - do not allow routing
    • MSG_OOB - send data as out of bound data. Move to the front of the receive queue.
    • MSG_PEEK - copy the data at the front of the queue, but do not remove it.
    • MSG_DONTWAIT - if there is nothing in the queue, return EAGAIN immediately.
  • return of -1 indicates an error
  • Otherwise return indicates the number of characters sent.
• recvfrom, recv, recvmsg
  • ssize_t recvfrom(int s, void *buf, size_t len, int flags, struct sock- addr *from, socklen_t *fromlen);
  • If from is NULL, the underlying protocol will fill in the results.
• UDP
  • You only need socket, and bind for the server
  • you can use sendto and recvfrom
• select
  • lets you look at a set of connections, and get the one that has had a change.
  • This would let you have a server, with a number of connections, and service all of them.
  • I knew how this worked once