LibCore+LookupServer: Implement and use UDPServer::send

Author: https://github.com/sin-ack
Commit: 0cca6cef95
Pull-request: https://github.com/SerenityOS/serenity/pull/9977
Reviewed-by: https://github.com/Dexesttp
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/awesomekling

Userland/Libraries/LibCore/UDPServer.cpp

@@ -102,4 +102,18 @@ Optional<u16> UDPServer::local_port() const
     return ntohs(address.sin_port);
 }
 
+ErrorOr<size_t> UDPServer::send(ReadonlyBytes buffer, sockaddr_in const& to)
+{
+    if (m_fd < 0) {
+        return Error::from_errno(EBADF);
+    }
+
+    auto result = ::sendto(m_fd, buffer.data(), buffer.size(), 0, (sockaddr const*)&to, sizeof(to));
+    if (result < 0) {
+        return Error::from_errno(errno);
+    }
+
+    return result;
+}
+
 }