How to read data (xml) sent by server if it doesn't send new line

问题

Let's say we try to communicate with a server (XMPP) which sends back XML data. We can use

conn, err := net.Dial("tcp", s.Addr+":5222")
//...
r := bufio.NewReader(conn)
//...
s, err := s.R.ReadString(10) // to read a string

But there is one problem that the server doesn't send the \10 (newline) symbol. I also tried 12 but without any luck. Same goes for readLine function as it also relies on \10. So how do I read the data sent by server? I tried using '>' as a delimiter and succeeded to receive only parts of the messages (predictable). I had an idea to loop while error is nil and use delimiter of '>' but it also didn't work. My research shown that the last symbol of the message is really '>' (62) and there is not any anything else at the end.

回答1:

Use an xml.Decoder to read stanzas from an XMPP stream.

conn, err := net.Dial("tcp", s.Addr+":5222")
if err != nil {
    // handle error
}
dec := xml.NewDecoder(conn)

Use the decoder Token method to read the root document element and to skip over character data between stanzas:

func readStartElement(dec *xml.Decoder) (xml.StartElement, error) {
    for {
        t, err := dec.Token()
        if err != nil {
            return xml.StartElement{}, err
        }
        switch t := t.(type) {
        case xml.StartElement:
            return t, nil
        }
    }
}

Use the decoder DecodeElement method to read a stanza:

func readStanza(dec *xml.Decoder) (interface{}, error) {
    se, err := readStartElement(dec)
    if err != nil {
        return nil, err
    }
    var v interface{}
    switch  se.Name.Space + " " + se.Name.Local {
    case "jabber:client message":
        v = &jabberMessage{} // jabberMessage is struct type defined by app for messages
    // Add other stanza types here.        
    default:
        v = &struct{}{}
    }
    if err := dec.DeocdeElement(v, &se); err != nil {
        return nil, err
    }
    return v, nil
}

Type switch on the return value from readStanza to handle the different types of received stanzas.

A client reads stanzas synchronously. Here's rough outline (ignoring authentication, etc).

conn, err := net.Dial("tcp", s.Addr+":5222")
if err != nil {
    // handle error
}
dec := xml.NewDecoder(conn)

// read and discard root element
_, err := readStartElement(dec)
if err != nil {
     // handle error
}

// read stanzas
for {
   v, err := readStanza(dec)
   if err != nil {
       // handle error 
       // must break out of loop on error
   }
   switch v := v.(type) {
   case *jabberMessage:
        // handle message
   case *someOtherStanzaType:
        // handle other stanza types
        // ... and so on
   }
}

来源：https://stackoverflow.com/questions/36105199/how-to-read-data-xml-sent-by-server-if-it-doesnt-send-new-line

标签

sockets

buffered