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tcp-echo-server.go
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tcp-echo-server.go
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// package main implements a TCP echo server that echoes back the TCP client's request as a part of its response.
package main
import (
"bufio"
"flag"
"fmt"
"io"
"net"
"strings"
"github.com/flomesh-io/fsm/pkg/logger"
)
var (
log = logger.NewPretty("tcp-echo-server")
logLevel = flag.String("logLevel", "debug", "Log output level")
port = flag.Int("port", 9090, "port on which this app is serving TCP connections")
responsePrefix = "echo response:"
)
func main() {
flag.Parse()
err := logger.SetLogLevel(*logLevel)
if err != nil {
log.Fatal().Msgf("Unknown log level: %s", *logLevel)
}
listenAddr := fmt.Sprintf(":%d", *port)
// Create a tcp listener
listener, err := net.Listen("tcp", listenAddr)
if err != nil {
log.Fatal().Err(err).Msgf("Error creating TCP listener on address %q", listenAddr)
}
log.Info().Msgf("Server listening on address %q", listenAddr)
// listen for new connections
for {
conn, err := listener.Accept()
if err != nil {
log.Error().Err(err).Msg("Error accepting connection")
continue
}
go echoResponse(conn)
}
}
func echoResponse(conn net.Conn) {
//nolint: errcheck
//#nosec G307
defer conn.Close()
reader := bufio.NewReader(conn)
for {
requestMsg, err := reader.ReadString(byte('\n'))
requestMsg = strings.TrimSuffix(requestMsg, "\n") // trim trailing newline character
switch err {
case nil:
// respond to the request, prepend the prefix to the response
log.Info().Msgf("Received request: [%s]", requestMsg)
response := fmt.Sprintf("%s %s\n", responsePrefix, requestMsg)
if bytesWritten, writeErr := conn.Write([]byte(response)); err != nil {
log.Error().Err(writeErr).Msg("Write error")
} else {
log.Debug().Msgf("Wrote %d bytes", bytesWritten)
}
log.Info().Msgf("Response sent: [%s]", response)
case io.EOF:
log.Debug().Msgf("EOF received")
return
default:
// unexpected error
log.Error().Err(err).Msgf("Unexpected error")
return
}
}
}