2016-11-29 09:28
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I do have a process receiving data from second local process. I need to test if connection errors are handled well AND if it automatically reconnects and keep receiving data after a disconnection.

To do so I am trying to make it disconnect abruptly or put the TCP connection in an error state from a unit test. As seen in this question to check if a connection is closed I am checking for data to come and test if it returns an error. I am not sure how to:

  • close the connection ungracefully
  • make it be in an error state

This is the essence of my data receiver:

    import (

    type Message struct {
        ID string `json:"id"`

    func ReceiveData(listener Listener) {
        var tcpConn net.Conn
        var addr string = ""
        tcpConn, err := net.Dial("tcp", addr)
        socketReader := bufio.NewReader(tcpConn)
        decoder := json.NewDecoder(socketReader)

        for {
            var msg Message
            if err := decoder.Decode(&msg); err == io.EOF {
                listener.ProcessUpdate(Message{}, fmt.Errorf("Received EOF"), nil)
                tcpConn = nil
            } else if err != nil {
                listener.ProcessUpdate(Message{}, nil, fmt.Errorf("Error decoding message: %s", err.Error()))
                tcpConn = nil

        // process message
        _ = msg

        // Test disconnection
        // This does not disconnect:
        // tcpConn = nil
        // This does but gracefully:
        // tcpConn.Close()

I am not mocking the TCP connection as I'd like to try with the real data producer. If is needed I'll look at it.

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1条回答 默认 最新

  • dongyu4455 2016-11-29 11:59

    A solution is to set a deadline to the TCP connection itself:


    Later this will trigger a timeout error which can be caught with:

    err := decoder.Decode(&msg);
    if err != nil {
        if neterr, ok := err.(net.Error); ok && neterr.Timeout() {
            fmt.Errorf("TCP timeout : %s", err.Error())
        } else {
            fmt.Errorf("Received error decoding message: %s", err.Error())
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