Handle 'connection reset by peer' error in Go

connection_reset_by_peer.go

package main

import (
	"errors"
	"log"
	"net"
	"os"
	"syscall"
	"time"
)

func server() {
	listener, err := net.Listen("tcp", ":8000")
	if err != nil {
		log.Fatal(err)
	}

	defer listener.Close()

	conn, err := listener.Accept()
	if err != nil {
		log.Fatal("server", err)
		os.Exit(1)
	}

	data := make([]byte, 1)
	if _, err := conn.Read(data); err != nil {
		log.Fatal("server", err)
	}

	conn.Close()
}

func client() {
	conn, err := net.Dial("tcp", "localhost:8000")
	if err != nil {
		log.Fatal("client", err)
	}

	if _, err := conn.Write([]byte("ab")); err != nil {
		log.Printf("client: %v", err)
	}

	time.Sleep(1 * time.Second) // wait for close on the server side

	data := make([]byte, 1)
	if _, err := conn.Read(data); err != nil {
		log.Printf("client: %v", err)
		if errors.Is(err, syscall.ECONNRESET) {
			log.Print("This is connection reset by peer error")
		}
	}
}

func main() {
	go server()

	time.Sleep(3 * time.Second) // wait for server to run

	client()
}

/*
Reproduce the connection reset by peer error

	We can reproduce the error by creating a server and client that do the following:
		1. the server reads a single byte and the closes the connection
		2. the client sends more than one byte

		If the server closes the connection with the remaining bytes in the socket's receive buffer,
		then an RST packet is sent to the client. When the client tries to read from such a closed connection,
		it will get the `connection reset by peer` error.
*/

Typically, you can see connection reset by peer error in response to a request being sent from the client to the server. It means that something bad has happended to the server: it has rebooted, the program has crashed, or other problems have occurred that cause the connection to be forcibly closed(强制关闭).

Since TCP connections can be broken, there is no needed to handle the connection reset by peer in any special way on the client side. You can log the error, ignore it or retry the connection when it occurs.

Difference between connection reset by peer and broken pipe

Both connection reset by peer and broken pipe errors occur when a peer (the other end) unexpectedly closes the underlying connection. However, there is a subtle difference between them. Usually, you get the connection reset by peer when you read from the connection after the server sends the RST packet, and when you write to the connection after the RST instead, you get the broken pipe error.