The protocol i am programming for sends a header of 8 bytes that contains a
body length.
My problem is dat c.Read(buf) is blocking. Can i read from the tcp
connection non blocking ?
On Wednesday, March 31, 2021 at 9:08:48 AM UTC+2 Brian Candler wrote:
> On Wednesday, 31 March 2021 at 04:13:12 UTC+1 matt....@gmail.com wrote:
>
>> for i := 0; i > 5; i++ {
>> // handle a single message
>> n, err := c.Read(buf)
>> if err == io.EOF {
>> break
>> }
>> fmt.Fprintf(c, "Message Count %d, Data %s", i+1, buf[:n])
>>
>
> I will point out that it's possible for io.Read to return valid data *and*
> an error (including io.EOF). See https://golang.org/pkg/io/#Reader
>
>
> *"When Read encounters an error or end-of-file condition after
> successfully reading n > 0 bytes, it returns the number of bytes read. It
> may return the (non-nil) error from the same call or return the error (and
> n == 0) from a subsequent call. An instance of this general case is that a
> Reader returning a non-zero number of bytes at the end of the input stream
> may return either err == EOF or err == nil. The next Read should return 0,
> EOF."*
>
> So perhaps you want something more like this:
>
> n, err := c.Read(buf)
> if n > 0 {
> fmt.Fprintf(c, "Message Count %d, Data %s", i+1, buf[:n])
> }
> if err == io.EOF {
> break
> }
> if err != nil {
> fmt.Fprintf("Error: %s", err)
> break
> }
>
> Note that TCP is stream-oriented, so the number of bytes returned from
>> Read is not at all guaranteed to match the number of bytes the client sent.
>> The returned data can be part of one or more messages. You need some other
>> mechanism to divide the data received into messages. For example you might
>> want to read a line at a time instead.
>>
>
> That's critical. Messages need to be delimited somehow. Some protocols
> send a length followed by that number of bytes of data. Note that the JSON
> encoder/decoder in go supports sending objects one after the other - that
> is, the structure of a JSON object performs the delineation. After the
> start of an object '{' the decoder will keep consuming data until it gets
> the matching close '}'
>
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