I am designing a mobile game, but I don't know much about it.
How do we differentiate HTTP, TCP and UDP in reference to mobile game?
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5\$\begingroup\$ The title of your question doesn't match the content of your question. Could you rephrase and be more specific as to what exactly you are designing, and what you need to know? \$\endgroup\$– KylotanCommented Apr 12, 2011 at 11:56
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1\$\begingroup\$ This could be a great question with even better answers, but its so poorly asked. Someone please rescue it. \$\endgroup\$– deft_codeCommented Apr 12, 2011 at 15:34
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\$\begingroup\$ Hi at least try to give the answer of poorly asked Question.. \$\endgroup\$– GameBuilderCommented Apr 12, 2011 at 15:38
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\$\begingroup\$ I think you should not distinguish between Mobile and Desktop. Protocols are the same everywhere, and I think that hardware performance is also pretty much the same. \$\endgroup\$– Ivan KuckirCommented Mar 21, 2013 at 0:01
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4 Answers
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HTTP is just another protocol on top of TCP, therefore I'll skip it in my answer. Use HTTP only for infrequent simple notifications like highscore uploads.
Beej has a good tutorial on TCP and UDP socket programming: http://beej.us/guide/bgnet/output/html/singlepage/bgnet.html
Basically TCP is a connection oriented protocol. A client connects to a server, they exchange some messages, one of them closes the connection. You can think of it as a bytestream flowing directly from one side to the other. TCP makes sure no byte gets lost and all of them arrive in order.
UDP doesn't provide anything of this. It is very low-level. You just send a bunch of bytes (message) to some destination (address). UDP will build a packet out of these and send it on its way. There is no guarantee it will ever arrive.
For high-performance multiplayer games you need UDP, because you can't afford the latency overhead of TCP. But you have to handle all of those cases where packets get lost, duplicated or reordered yourself.
If latency is not of concern go for TCP. It is much easier to use.
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\$\begingroup\$ Thanks of the answer.. I will tell more detail about the game. I have to design PONG game in android.There are 2 mobiles and 1 game server.Application is installed in mobile .In mobile1(M1) can see the movement of bat and ball of Mobile2(M2) an vice_versa.Suppose if M1 hits the ball,all the movements of the ball and bat of M1 can be seen in M2 Screen and viceversa. Now i want to know which protocol i should use and why. \$\endgroup\$ Commented Apr 12, 2011 at 15:28
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1\$\begingroup\$ Why do you find TCP easier? A stream flow is logically more complex to handle than single definite packets. If you consider UDP difficult because you want it to actually be TCP, well, you should be using TCP in the first place instead. \$\endgroup\$– o0'.Commented Sep 29, 2011 at 9:52
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\$\begingroup\$ why would TCP have bigger latency? if you have an established TCP connection, latency should not be worse than UDP. Packet loss is the real concern (which is problematic in wireless environments), latency is in this case just a consequence in TCP because of the built in retry mechanism. But the real issue is loss, which is noticeable also for UDP (and should be handled) \$\endgroup\$– user8357Commented Mar 20, 2013 at 20:57
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1\$\begingroup\$ @KillianDS UDP doesn't only mean packet loss. You also have to handle dup packets, out of order, spoofed, neatly constructed fragments trying to smash your protocol stack. Do you really want to do this? \$\endgroup\$– ott--Commented Mar 20, 2013 at 21:33
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\$\begingroup\$ @ott-- and where does this contradict what I say? I know UDP-based protocols are a disaster to get right (I work with them day-to-day). I just show that latency itself is not different between UDP and TCP, it is usually just the consequence of packet loss. Of course there are other reasons, if you set up a TCP connection for each message your latency will be bad too, but that's just plain stupid. \$\endgroup\$– user8357Commented Mar 20, 2013 at 21:47
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On Stack Overflow there's an answer that says that mobile carriers don't allow UDP:
https://stackoverflow.com/questions/5861009/realtime-multiplayer-game-over-mobile-network
That would appear to make it open and shut: only TCP is viable, if that answer is correct.
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One key difference between UDP and TCP is, for lack of a better phrase, "ownership of receipt".
In UDP the receiver is responsible for guaranteeing receipt of all required messages. This is particularly useful for streaming media content, becuase in most cases if a message is lost the receiver doesn't care; the frame is past history and had a spot of snow. No harm no foul.
In TCP the sender is responsible for guaranteeing delivery, so if no acknowledement is received before timeout the message is resent. There is greater overhead on both sides, plus greater traffic in the form of all the acknowledgements; but the benefit is a more reliable delivery.
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UDP is difficult; you can typically only use UDP for client-initiated messages.
Also, TCP is also particularly high latency for mobile. And its very bursty; it might be running very fast and suddenly it drops right off.
But TCP works pretty much across the board.
There is no widespread peer-to-peer networking for games; all gets bounced through a central server.
You can do fun peer-to-peer stuff using any platform-provided push mechanism e.g. C2DM on Android, but that only suits turn-based slow games.
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\$\begingroup\$ Thanks of the answer.. I will tell more detail about the game. I have to design PONG game in android.There are 2 mobiles and 1 game server.Application is installed in mobile .In mobile1(M1) can see the movement of bat and ball of Mobile2(M2) an vice_versa.Suppose if M1 hits the ball,all the movements of the ball and bat of M1 can be seen in M2 Screen and vice versa. Now i want to know which protocol i should use and why. \$\endgroup\$ Commented Apr 12, 2011 at 15:27
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1\$\begingroup\$ What would be difficult about UDP? \$\endgroup\$– o0'.Commented Sep 29, 2011 at 9:51
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\$\begingroup\$ > you can typically only use UDP for client-initiated messages \$\endgroup\$– WillCommented Sep 29, 2011 at 10:18
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1\$\begingroup\$ Have you ever even used UDP? \$\endgroup\$ Commented Mar 21, 2013 at 3:24