First of all, is there any problem with using both UDP and TCP on the same server?
Secondly, can I use the same port number?
Yes, you can use the same port number for both TCP and UDP. Many protocols already do this, for example DNS works on udp/53 and tcp/53.
Technically the port pools for each protocol are completely independent, but for higher level protocols that can use either TCP or UDP it's convention that they default to the same port number.
When writing your server, bear in mind that the sequence of events for a TCP socket is much harder than for a UDP socket, since as well as the normal socket and bind calls you also have to listen and accept.
Furthermore that accept call will return a new socket and it's that socket that you'll then have to also poll for receive events. Your server should be prepared to continue accepting connections on the original socket whilst simultaneously servicing multiple clients each of which will be triggering receive events on their own sockets.
Firstly,there is no problem using both tcp and udp on the server.
Secondly,we can have both UDP and TCP requests on same port ,because each request is identified by a quintuple contained by source IP ,Destination IP, Source Port, Destination Port, PROTOCOL(as protocol can be TCP or UDP).
Related
Please assume that we can distinguish packets of different TCP connections from each other, if so then can we accept multiple TCP connections on the only one socket in server side? I know that the server binds on a socket and when accepting new connection assigns a new socket to new connection. Would I override ACCEPT systemcall?
Please assume that we can distinguish packets of different TCP connections from each other
You can't assume it. There are no 'packets' visible to the application over a TCP connection. A TCP connection provides a byte stream. You can't guarantee that the next thing you read will be say a message header telling you which client the message is from.
I'm working on a program in which a UDP server keeps listening to incoming requests.
If a particluar kind of request is received, it tries to create a RMI server using the same port on which the UDP server was listening.
So, is this possible?
or I need to have different ports?
Yes it's possible. TCP and UDP port numbers are in different namespaces.
I have the following statement.
"In TCP, the receiver host uses all of source IP, source port, destination IP and destination port to direct datagram to appropriate socket. While in UDP, the receiver only checks destination port number to direct the datagram. "
Is the above statement true?
If yes, does it mean that in TCP the same port can be used for multiple socket in one process, while in UDP only one socket can use on a port in one process? What about sockets in different processes? Can multiple processes use the same port in TCP/UDP? (in programming language: C/C++/Java)
If not, why?
"In TCP, the receiver host uses all of source IP, source port, destination IP and destination port to direct datagram to appropriate socket. While in UDP, the receiver only checks destination port number to direct the datagram. "
Is the above statement true?
Yes.
If yes, does it mean that in TCP the same port can be used for multiple socket in one process,
Yes, under some circumstances.
while in UDP only one socket can use on a port in one process?
No, see below.
What about sockets in different processes? Can multiple processes use the same port in TCP/UDP? (in programming language: C/C++/Java)
Under some circumstances, yes. A UDP port has to be designated as reusable by all processes that want to share it. A TCP port can only be reused by sockets bound to different interfaces: there is no sharing.
What that means is, in TCP, a unique communication "channel" can be described as the four-tuple: (src-ip, src-port, dst-ip, dst-port).
In UDP, all packets destined to a certain port are delivered to the only UDP socket listening on that port, regardless of the source address and port of said packet. I like to think of it as a funnel.
I'm creating a socket table from a network composed of 2 hosts. They have a p2p connection and they're working with tcp protocol. Do I have to create a welcoming socket in both of the hosts (as they act like servers)? And a receiving socket as well as a sending socket for each host? Or just one for sending/receiving would be ok?
Each host will need a listening socket on which it will accept new connections. It will also need one socket for each inbound TCP connection (returned from the accept call when it accepts an inbound connection) and one for each outbound TCP connection (returned from the socket call before calling connect to make the outbound connection).
I know you can't have two different process using the same port, but what happens if one is using tcp and the other one udp? Can you have two different process each one binding a socket to the same port but different protocol?
The 5-tuple (protocol, source ip, source port, dest ip, dest port) must be unique. That means that not only can you have TCP and UDP using the same port number, but even outgoing connections with the same protocol and local port number, but different destinations.
When listening however, sockets usually must be unique in their protocol, i.e. you can/should not open another TCP socket with the same port number.
TCP ports and UDP ports are not related to each other at all.
Yes. Two sockets can bind same port number but different protocol.
It's not the same port, just happens to have the same number.