TCP连接似乎一次读取太多字节

Question

I'm writing an FTP server in Go and I've run into a problem when listing the files/directories. What seems to be happening is that the server is sending the files each separately and correctly but when reading them from the connection, they get read multiple at a time.

I've tried changing the buffer size as well as sending a confirmation before sending each file name yet when reading from the connection it ends up reading more bytes than expected.

This is the relative part from the server:

for _, fn := range files {
    conn.Write([]byte(fn.Name()))
}

In the code above, files is []os.FileInfo from ioutil.ReadDir("./") to get the files in the current directory. When tested this sends the correct file name as well as the correct bytes for each name.

On the client I have this:

var buf [256]byte
for i := 0; i < int(amnt); i++ {
    n, err = conn.Read(buf[:])
    if err != nil {
        fmt.Printf("Error getting files: %s
", err)
    }
    fmt.Printf("%s
", string(buf[:n]))
}

int(amnt) is just an int for how many files are in the directory and is correct.

The server sends everything correctly so I am sure that the problem lies in reading into buf but I can't figure out why it would be reading in more than one file name at a time.

Answer 1

One strategy to address this could be to develop a loose structured protocol which will involve having the client delineate files and the server parse files. This might be done by sending a new line after each file that the client writes. This way the server can scan lines from the TCP connection using go's Scanner:

for _, fn := range files {
    conn.Write([]byte(fn.Name()))
    conn.Write([]byte(`
`))
}

scanner := bufio.NewScanner(conn)
for {
        if ok := scanner.Scan(); !ok {
            break
        }
        fmt.Println(scanner.Text())
    }
    fmt.Println("Scanning ended")

---

Go makes this possible because the TCP connection implements the io.Reader interface.