Call TCP send (net package) from http request function

user_1949724 0
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I'm new to Go - following problem: My program receives an http post request and now I want to forward data from it to an active TCP connection (the program runs a parallel TCP Server). In main() the handler is registered like this: http.HandleFunc("/rcvtelegram", handleRestRequest)

and the http-handler function is therefore like this:

func handleRestRequest(w http.ResponseWriter, r *http.Request) {}

The TCP connection to the client is open with a net.Conn object which main() knows. So ideally I would start a go routine with a TCP sender function that listens for an incoming string to send it through TCP. But how? With channels it seems I must pass all parameters but I don't have the connection object in the http handler function. I also want to avoid making the tcp connection a global variable. I saw the Observer pattern but that scares me with its complexity as a newbie (and not sure if it solves my problem).

Thanks!

go
2 Answers

Use a struct type to hold the channel. Implement the http.Handler interface on the type:

type RestHandler struct {
    ch chan string
}

func (h *RestHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {
    // insert body of the handleRestRequest here.
    // Use h.ch <- someString to send string to connection
}

In your main function, create a channel for the TCP sender and start the sender in a goroutine:

ch := make(chan string)
go tcpSender(ch)

Create a value of *RestHandler with the channel and register it as the handler:

http.Handle("/rcvtelegram", &RestHandler{ch:ch})
user_191745250

Based on above proposal I built it this way:

type TcpHandler struct {
    connection net.Conn
}

Then defined a custom HTTP Handler:

func (t TcpHandler) ServeHTTP(w http.ResponseWriter, r *http.Request) {...}

Then registered it with the existing TCP connection in main():

httpTcpHandler := TcpHandler{connection: conn}
mux := http.NewServeMux()
mux.Handle("/rcvtelegram", httpTcpHandler)
go startHttpServer(httpPort, mux)

Works as it should! I like programming in Go more and more

user_19497240
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