Multiple serial requests result in empty buffer - go

Question

The first TCP connection running on localhost on osx always parses the binary sent to it correctly. Subsequent requests lose the binary data, only seeing the first byte [8]. How have I failed to set up my Reader?
package main
import (
"fmt"
"log"
"net"
"os"
"app/src/internal/handler"
"github.com/golang-collections/collections/stack"
)
func main() {
port := os.Getenv("SERVER_PORT")
s := stack.New()
ln, err := net.Listen("tcp", ":8080")
if err != nil {
log.Fatalf("net.Listen: %v", err)
}
fmt.Println("Serving on " + port)
for {
conn, err := ln.Accept()
// defer conn.Close()
if err != nil {
log.Fatal("ln.Accept")
}
go handler.Handle(conn, s)
}
}
package handler
import (
"fmt"
"io"
"log"
"net"
"github.com/golang-collections/collections/stack"
)
func Handle(c net.Conn, s *stack.Stack) {
fmt.Printf("Serving %s\n", c.RemoteAddr().String())
buf := make([]byte, 0, 256)
tmp := make([]byte, 128)
n, err := c.Read(tmp)
if err != nil {
if err != io.EOF {
log.Fatalf("connection Read() %v", err)
}
return
}
buf = append(buf, tmp[:n]...)
}
log:
Serving [::1]:51699
------------- value ---------------:QCXhoy5t
Buffer Length: 9. First Value: 8
Serving [::1]:51700
------------- value ---------------:
Buffer Length: 1. First Value: 8
Serving [::1]:51701
test sent over:
push random string:
QCXhoy5t
push random string:
GPh0EnbS
push random string:
4kJ0wN0R

Answer 1

The docs for Reader say:
Read reads up to len(p) bytes into p. It returns the number of bytes read (0 <= n
<= len(p)) and any error encountered. Even if Read returns n < len(p), it may use
all of p as scratch space during the call. If some data is available but not
len(p) bytes, Read conventionally returns what is available instead of waiting
for more.
So the most likely cause of your issue is that Read is returning the data available (in this case a single character). You can fix this by using ioutil.ReadAll or performing the read in a loop (the fact the data is being added to a buffer makes it look like that was the original intention) with something like:
for {
n, err := c.Read(tmp)
if err != nil {
if err != io.EOF {
// Note that data might have also been received - you should process that
// if appropriate.
log.Fatalf("connection Read() %v", err)
return
}
break // All data received so process it
}
buf = append(buf, tmp[:n]...)
}
Note: There is no guarantee that any data is received; you should check the length before trying to access it (i.e. buf[0] may panic)