├── go.mod
├── .gitignore
├── README.md
└── cmd
    └── main.go


/go.mod:
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1 | module github.com/nats-logger
2 | 
3 | go 1.17
4 | 


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/.gitignore:
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 1 | # Binaries for programs and plugins
 2 | *.exe
 3 | *.exe~
 4 | *.dll
 5 | *.so
 6 | *.dylib
 7 | 
 8 | # Test binary, built with `go test -c`
 9 | *.test
10 | 
11 | # Output of the go coverage tool, specifically when used with LiteIDE
12 | *.out
13 | 
14 | # Dependency directories (remove the comment below to include it)
15 | # vendor/
16 | 
17 | # Tools
18 | .idea
19 | .vscode
20 | 


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/README.md:
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 1 | # NATS Logger
 2 | 
 3 | NATS uses a simple publish/subscribe style plain-text protocol to communicate between a NATS Server and its clients. Whilst this connection should remain opaque to the user, it can be quite handy to see the data being passed from time to time - this tool does just that (it also saves me loading Wireshark and filtering the NATS traffic). 
 4 | 
 5 | More information on NATS connection protocol can be found [here](https://docs.nats.io/reference/reference-protocols/nats-protocol).
 6 |     
 7 | <img width="1338" alt="screenshot" src="https://user-images.githubusercontent.com/1237341/149612435-6cdfac10-44ac-4bd9-8e4f-d8464893a235.png">
 8 | 
 9 | ## Next step...
10 | 
11 | Next step is to add support for printing a pretty print version to a web UI over websockets.
12 | 


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/cmd/main.go:
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 1 | package main
 2 | 
 3 | import (
 4 | 	"flag"
 5 | 	"fmt"
 6 | 	"io"
 7 | 	"log"
 8 | 	"net"
 9 | )
10 | 
11 | var (
12 | 	localAddr  = flag.String("l", "localhost:9999", "Local address")
13 | 	remoteAddr = flag.String("r", "localhost:5222", "NATS Server address")
14 | )
15 | 
16 | func main() {
17 | 
18 | 	flag.Parse()
19 | 	fmt.Printf("Listening: %v\nProxying: %v\n\n", *localAddr, *remoteAddr)
20 | 
21 | 	listener, err := net.Listen("tcp", *localAddr)
22 | 	if err != nil {
23 | 		panic(err)
24 | 	}
25 | 	for {
26 | 		localConn, err := listener.Accept()
27 | 		log.Println("New connection", localConn.RemoteAddr())
28 | 		if err != nil {
29 | 			log.Println("error accepting connection", err)
30 | 			continue
31 | 		}
32 | 		go func() {
33 | 			defer localConn.Close()
34 | 			natsConn, err := net.Dial("tcp", *remoteAddr)
35 | 			if err != nil {
36 | 				log.Println("error dialing remote addr", err)
37 | 				return
38 | 			}
39 | 			defer natsConn.Close()
40 | 			closer := make(chan struct{}, 2)
41 | 
42 | 			go copy(closer, natsConn, io.TeeReader(localConn, logger("server")))
43 | 			go copy(closer, localConn, io.TeeReader(localConn, logger("client")))
44 | 
45 | 			//go copy(closer, natsConn, localConn)
46 | 			//go copy(closer, localConn, natsConn)
47 | 
48 | 			<-closer
49 | 			log.Println("Connection complete", localConn.RemoteAddr())
50 | 		}()
51 | 
52 | 	}
53 | 
54 | }
55 | 
56 | type logger string
57 | 
58 | func (lh logger) Write(b []byte) (int, error) {
59 | 	fmt.Printf(string(b))
60 | 	return len(b), nil
61 | }
62 | 
63 | func copy(closer chan struct{}, dst io.Writer, src io.Reader) {
64 | 	_, _ = io.Copy(dst, src)
65 | 	closer <- struct{}{} // connection is closed, send signal to stop proxy
66 | }
67 | 


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