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| <h4 class="subsection">16.10.3 Datagram Socket Example</h4> |
| |
| <p>Here is a set of example programs that send messages over a datagram |
| stream in the local namespace. Both the client and server programs use |
| the <code>make_named_socket</code> function that was presented in <a href="Local-Socket-Example.html#Local-Socket-Example">Local Socket Example</a>, to create and name their sockets. |
| |
| <p>First, here is the server program. It sits in a loop waiting for |
| messages to arrive, bouncing each message back to the sender. |
| Obviously this isn't a particularly useful program, but it does show |
| the general ideas involved. |
| |
| <pre class="smallexample"> #include <stdio.h> |
| #include <errno.h> |
| #include <stdlib.h> |
| #include <sys/socket.h> |
| #include <sys/un.h> |
| |
| #define SERVER "/tmp/serversocket" |
| #define MAXMSG 512 |
| |
| int |
| main (void) |
| { |
| int sock; |
| char message[MAXMSG]; |
| struct sockaddr_un name; |
| size_t size; |
| int nbytes; |
| |
| /* <span class="roman">Remove the filename first, it's ok if the call fails</span> */ |
| unlink (SERVER); |
| |
| /* <span class="roman">Make the socket, then loop endlessly.</span> */ |
| sock = make_named_socket (SERVER); |
| while (1) |
| { |
| /* <span class="roman">Wait for a datagram.</span> */ |
| size = sizeof (name); |
| nbytes = recvfrom (sock, message, MAXMSG, 0, |
| (struct sockaddr *) & name, &size); |
| if (nbytes < 0) |
| { |
| perror ("recfrom (server)"); |
| exit (EXIT_FAILURE); |
| } |
| |
| /* <span class="roman">Give a diagnostic message.</span> */ |
| fprintf (stderr, "Server: got message: %s\n", message); |
| |
| /* <span class="roman">Bounce the message back to the sender.</span> */ |
| nbytes = sendto (sock, message, nbytes, 0, |
| (struct sockaddr *) & name, size); |
| if (nbytes < 0) |
| { |
| perror ("sendto (server)"); |
| exit (EXIT_FAILURE); |
| } |
| } |
| } |
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