I'm new to Golang and this kind of more lowlevel stuff, so maybe i'm just thinking in the wrong direction.
My project is a small golang monitoring client which sends some ping-message (current date) over a encrypted TLS connection (this is just for learning purpose). The python server and client are working flawless for now.
The (python) server & client are packing the data like this:
[...]
def _send_msg(self, msg):
msg = struct.pack('>I', len(msg)) + bytes(msg, 'UTF-8')
self.client.send(msg)
def _recv_msg(self):
raw_msglen = self.client.recv(4)
if not raw_msglen:
return ""
msglen = struct.unpack('>I', raw_msglen)[0]
return self._recvall(msglen)
[...]
On the Go-Side I pack the data like this:
type packet struct {
a uint32
b []byte
}
func pack(d string) []byte {
buf := bytes.Buffer{}
u := len([]byte(d))
p := packet{
a: uint32(u),
b: []byte(d),
}
err := binary.Write(&buf, binary.BigEndian, p.a) // struct.unpack('>I' [...] in python
if err != nil {
fmt.Println(err)
}
buf.Write(p.b) // Append bytes to buffer
return buf.Bytes()
}
reader := bufio.NewReader(tlsConn) // Socket reader
[..]
// Writing binary data
tlsConn.Write(pack("login test:test")) // Works so far
// Reading response (from python server)
var p uint32 // packet size
binary.Read(reader, binary.BigEndian, &p) // Read packet length (4 bytes uint32)
buf1 := make([]byte, int(p))
reader.Read(buf1)
fmt.Println(string(buf1)) // Print response - this also works
// Send some ping
// This code part also get's passed, but the python server doesn't
// recive any message
c.Write(pack("ping 0000-00-00 00:00:00"))
binary.Read(reader, binary.BigEndian, &p)
buf1 = make([]byte, int(p))
fmt.Println(string(buf1)) // Here i don't get an response
Here is the golang client-side test code which I'm using: http://pastebin.com/dr1mJZ9Y and the corresponding terminal output: http://pastebin.com/mrctJPs5
The strange thing is, that the login message (including the server response) all get sent (and received) correctly but the second time when i try to send a ping like:
tlsConn.Write(pack("ping 0000-00-00 00:00:00"))
The message seems not to reach the server and no response message gets send back to the client.
Is there an error with the binary encoding of the packet-data and the length prefixing?
I know the code looks a bit messy and not very go-idiomatic, sorry for that. Thank you again in advance for your help!
Software dependencies / environment:
- Python 3.4
- Golang 1.5.3 (amd64 Linux)
- No 3rd-Party libs
