How to catch server side errors for jsonrpc server?

php editor Zimo will introduce you how to capture server-side errors of the jsonrpc server. During the development process, server-side errors are often encountered, and it is very important to accurately capture these errors. To solve this problem, we can use try-catch statements to capture server-side errors and return error information to the client. In this way, we can better locate and handle server-side errors and improve program stability and reliability. In the following we will explain in detail how to achieve this process.

Question content

Suppose I have a basic golang jrpc server based on tcp:

package main

import (
    "fmt"
    "net"
    "net/rpc"
    "net/rpc/jsonrpc"
)

type Arith int

type Args struct {
    A, B int
}

func (t *Arith) Add(args *Args, result *int) error {
    *result = args.A + args.B
    return nil
}

func RunServer() {
    arith := new(Arith)
    rpc.Register(arith)

    listener, err := net.Listen("tcp", ":8080")
    if err != nil {
        fmt.Println("Error starting server:", err)
        return
    }
    defer listener.Close()

    for {
        conn, err := listener.Accept()
        if err != nil {
            fmt.Println("Error accepting connection:", err)
            continue
        }

        go jsonrpc.ServeConn(conn)
    }
}

Is there a way to print "Client disconnected!" when the client disconnects from the server? Is there a callback or something similar on net.Conn?

func main() {
    go RunServer()
    client, err := jsonrpc.Dial("tcp", "localhost:8080")
    if err != nil {
        fmt.Println("Error connecting to server:", err)
        return
    }
    

    args := &Args{A: 3, B: 5}
    var result int
    
    // run a method
    err = client.Call("Arith.Add", args, &result)
    if err != nil {
        fmt.Println("Error calling Add method:", err)
        return
    }
    fmt.Printf("Result of %d + %d = %d\n", args.A, args.B, result)
    
    // suppose the client closes the client
    client.Close()
    // how does the server detect that the client is closed?
    // would be nice if I could print "client disconnected!"
    // without having to send jsonrpc heartbeats

}

It would be nice if I didn't have to send jsonrpc heartbeat messages.

I tried periodically dummy reading from the conn in the goroutine, but this interferes with the jsonrpc connection.

Solution

The jsonrpc.ServeConn method returns when the client hangs up. Prints a "client disconnected" message after ServeConn returns.

func RunServer() {
    arith := new(Arith)
    rpc.Register(arith)

    listener, err := net.Listen("tcp", ":8080")
    if err != nil {
        fmt.Println("Error starting server:", err)
        return
    }
    defer listener.Close()

    for {
        conn, err := listener.Accept()
        if err != nil {
            fmt.Println("Error accepting connection:", err)
            continue
        }

        go func() {
           jsonrpc.ServeConn(conn)
           fmt.Println("client disconnected") // <--- new code here
        }()
    }
}

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