I will look into other protocols, although for now the performance is not an issue in servers with less than 100 players.
The problem with io.MultiWriter is that a player inside the group may disconnect or a new player may come in. This means a new io.MultiWriter must be created each time you dispatch, since the group may have changed in the meantime. This would also need a new encoder and then the "duplicate type received" happens. On Wed, 23 Dec 2020, 19:58 'Axel Wagner' via golang-nuts, < golang-nuts@googlegroups.com> wrote: > The issue with that approach is that gob keeps state about which > type-information it still has to send. So if you encode to, say, a > bytes.Buffer, it would encode all type-info on every message sent, which is > a significant overhead. > TBH, I don't understand why `io.MultiWriter` wouldn't work. It would be > helpful to see the code that causes the error message OP is seeing. > > However, really, gob just doesn't provide a good API for this sorta thing, > as mentioned. The format itself is fine, but the stateful connection means > that if you don't want to write *exactly* the same data in exactly the same > order to all connections (which can perform poorly and lead to operational > problems with timeouts and intermittently lost connections and the like), > you are going to have a bad time. > You honestly would fare better with a full-fledged RPC framework such as > gRPC. Or, if you don't want the overhead of its IDL, even json. Because at > least the "encode once, send to each client" is trivial to solve with that. > > But, that's just my 2¢ :) > > On Wed, Dec 23, 2020 at 11:43 PM Robert Engels <reng...@ix.netcom.com> > wrote: > >> Yes, that is why you need to create your own protocol. Use the gob to >> encode to a buffer then send the buffer on each of the connections using >> your protocol. >> >> On Dec 23, 2020, at 4:19 PM, Matthew Zimmerman <mzimmer...@gmail.com> >> wrote: >> >> >> My understanding is that gob streams are unique. >> >> From https://golang.org/pkg/encoding/gob/ >> "A stream of gobs is self-describing. Each data item in the stream is >> preceded by a specification of its type, expressed in terms of a small set >> of predefined types." >> >> In my own rudimentary understanding/terms, it sends the struct definition >> once, then uses shorthand for it afterwards. E.g, how many bytes and what >> order. If you mix and match streams that send definitions in different >> orders, then chaos ensues. >> >> I think this is why people use other encoders in the scenario you're >> taking about. For a one to one stream gob works great, but in this multi >> scenario I don't think it does. >> >> Matt >> >> On Wed, Dec 23, 2020, 5:07 PM Artur Vianna <lordhowen...@gmail.com> >> wrote: >> >>> If i create a bytes.Buffer and a gob.Encoder, each time i write to a >>> group of connections i get "duplicate type received" and if i try and reuse >>> the encoder, i get "corrupted data" and "unknown type". >>> It seems i can't use both net.Conn.Write and gob.Encoder.Encode in the >>> same connection, i will try always encoding to a buffer in both unicast and >>> multicast like you said and report if it works. >>> >>> On Wed, 23 Dec 2020, 18:49 Robert Engels, <reng...@ix.netcom.com> wrote: >>> >>>> You need to encode once to a byte array then send the byte array on >>>> each connection. >>>> >>>> On Dec 23, 2020, at 3:45 PM, meera <lordhowen...@gmail.com> wrote: >>>> >>>> >>>> I am trying to create a package for game servers using gob. The current >>>> approach is an application level multicasting over TCP, having a gob >>>> encoder and decoder for each player connection, and set up a goroutine to >>>> receive and another to dispatch for each one. The code for the dispatcher >>>> is here. But summarized, it simply receives data from a channel and encodes >>>> it. >>>> >>>> The problem is that if i want to transmit a single piece of data to all >>>> players, this piece of data is encoded again and again for each connection, >>>> doing duplicate work. With less than 100 players this is not a problem, but >>>> with 300+ my machine is at almost 100% usage and the profiler shows that >>>> most of it is spent on encoding. Here's the issue on github. >>>> >>>> I tryied using a io.MultiWriter but gob complains of duplicate type >>>> received, and if i try to write the raw bytes from the gob.Encoder i get >>>> corrupted data. An option is using UDP Broadcasting but since gob expects a >>>> stream, i'm affraid i will run into unexpected behavior when packets start >>>> to be lost and fragmented. >>>> >>>> Does gob expect a single encoder and decoder to own the stream? Not >>>> allowing two encoders on the server for one decoder on the client? >>>> >>>> -- >>>> You received this message because you are subscribed to the Google >>>> Groups "golang-nuts" group. >>>> To unsubscribe from this group and stop receiving emails from it, send >>>> an email to golang-nuts+unsubscr...@googlegroups.com. >>>> To view this discussion on the web visit >>>> https://groups.google.com/d/msgid/golang-nuts/0562184e-bbcc-44c9-adbf-37e8d5411c7cn%40googlegroups.com >>>> <https://groups.google.com/d/msgid/golang-nuts/0562184e-bbcc-44c9-adbf-37e8d5411c7cn%40googlegroups.com?utm_medium=email&utm_source=footer> >>>> . >>>> >>>> -- >>> You received this message because you are subscribed to the Google >>> Groups "golang-nuts" group. >>> To unsubscribe from this group and stop receiving emails from it, send >>> an email to golang-nuts+unsubscr...@googlegroups.com. >>> To view this discussion on the web visit >>> https://groups.google.com/d/msgid/golang-nuts/CAE%3DAWBXN46idvqUbCsGs%2BZbZt%2BCj4MowJ4Ozj3_U9_6-68OWDw%40mail.gmail.com >>> <https://groups.google.com/d/msgid/golang-nuts/CAE%3DAWBXN46idvqUbCsGs%2BZbZt%2BCj4MowJ4Ozj3_U9_6-68OWDw%40mail.gmail.com?utm_medium=email&utm_source=footer> >>> . >>> >> -- >> You received this message because you are subscribed to the Google Groups >> "golang-nuts" group. >> To unsubscribe from this group and stop receiving emails from it, send an >> email to golang-nuts+unsubscr...@googlegroups.com. >> To view this discussion on the web visit >> https://groups.google.com/d/msgid/golang-nuts/214752B6-2666-4892-A9B8-E4BC4127FD42%40ix.netcom.com >> <https://groups.google.com/d/msgid/golang-nuts/214752B6-2666-4892-A9B8-E4BC4127FD42%40ix.netcom.com?utm_medium=email&utm_source=footer> >> . >> > -- > You received this message because you are subscribed to the Google Groups > "golang-nuts" group. > To unsubscribe from this group and stop receiving emails from it, send an > email to golang-nuts+unsubscr...@googlegroups.com. > To view this discussion on the web visit > https://groups.google.com/d/msgid/golang-nuts/CAEkBMfGWtULh8Q3Jqu_gq5m5Si4PvJ1oVSZY7DVhu%3D6hGK83bg%40mail.gmail.com > <https://groups.google.com/d/msgid/golang-nuts/CAEkBMfGWtULh8Q3Jqu_gq5m5Si4PvJ1oVSZY7DVhu%3D6hGK83bg%40mail.gmail.com?utm_medium=email&utm_source=footer> > . > -- You received this message because you are subscribed to the Google Groups "golang-nuts" group. 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