CODEWITHSUNDEEP
clinuxsocketsudp
HacHac
HacHac

Reputation: 147

UDP - Multi-server single client

I have a linux computer with a code in C that must communicate in UDP with 4 differents equipments. The computer sends differents commands to each equipment and receives responses, sometimes in parallel ...

I am a perfect beginner, and managed to communicate with one equipment using UDP socket. But now, i'm looking for a way to communicate with all these equipments, what i would like to call "multiple socket", but i don't know where to look/ what word to search to find a way ...

My linux computer is the client and all the equipment servers. I only have one eth port on the computer and will have to use a switch to have access to all the equipment. I would like to create functions like :

sendcmd(IPnumber, PORTnumber, cmd , ...)
readbuff(IPnumber, PORTnumber, buff, ...)

so i can choose which IP will received cmd ... i don't know if it's possible or if i need to open the socket, then close and redo the operation with another IP ...

So, if I ever managed to make myself understood, where should I look for a solution to my problem?

Thank you !

Upvotes: 1

Views: 2308

Answers (1)

Johannes Overmann
Johannes Overmann

Reputation: 5160

You can use a single UDP socket for your scenario. You can keep the socket open for the lifetime of your application.

UDP is not connection oriented. UDP sockets are also not classified into client sockets and server sockets. UDP sockets are always bound to a local port, either implicitly (typically for pure clients) or explicitly (which is usually the case for servers). In your case you do not care about the port for your UDP client.

To send to your four UDP server you can use sendto(). This lets you specify the destination IP address and port the UDP packet gets sent to.

To receive from your four UDP servers you can use recvfrom(). This will tell the IP address and port where the UDP packet came from.

You most likely want to have a receive loop of some kind. If you want to do anything else in your application you most likely want to either make recvfrom() non-blocking or you want to have the receive loop in its own thread. But this goes beyond your question.

The most important aspect of UDP is that it is not a protocol (despite its name which is misleading). It is one puzzle piece for a protocol. It is a tool to develop your own protocol. But I assume you already have a specific protocol at hand defined by your peripherals.

Upvotes: 1

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