[Ginto8]

len is the number of bytes read by that specific call. Since there isn't always enough new data available to fill your buffer, read() lets you know exactly how much was there (or, more correctly, how much it copied into your buffer).

UDP is faster, but it's also a good bit riskier. TCP is nice because it guarantees that packets will arrive, that packets will not be corrupted, and that packets will arrive in the order they were sent. UDP guarantees nothing. However, since UDP doesn't have all those checks, it will be faster. Be careful using it, though, because you can no longer rely on any of the guarantees of TCP.