Golang udp server 2

package main

import (
    "fmt"
    "net"
    "os"
    "strconv"
    "strings"
    "sync"
)

func main() {
    // Check for valid command line arguments
    if len(os.Args) != 2 {
        fmt.Fprintf(os.Stderr, "Usage: %s <ip>:<port_range>\n", os.Args[0])
        os.Exit(1)
    }

    // Parse the IP address and port range
    ipAndPorts := os.Args[1]
    host, ports, err := net.SplitHostPort(ipAndPorts)
    if err != nil {
        fmt.Fprintf(os.Stderr, "Error parsing IP and port range: %v\n", err)
        os.Exit(1)
    }

    // Convert the port range to integers
    start, end := parsePortRange(ports)

    // Calculate the number of file chunks to send
    numChunks := 20 // replace with your own value
    chunksPerPort := numChunks / (end - start + 1)
    remainder := numChunks % (end - start + 1)

    // Open the file to be sent
    file, err := os.Open("path/to/file")
    if err != nil {
        fmt.Fprintf(os.Stderr, "Error opening file: %v\n", err)
        os.Exit(1)
    }
    defer file.Close()

    // Set up a wait group for the goroutines
    var wg sync.WaitGroup

    // Send file chunks to each port in the range concurrently
    for port := start; port <= end; port++ {
        wg.Add(1)
        go func(p int) {
            defer wg.Done()
            numChunksToSend := chunksPerPort
            if remainder > 0 {
                numChunksToSend++
                remainder--
            }
            sendFileChunks(host, p, file, numChunksToSend)
        }(port)
    }

    // Wait for all goroutines to finish
    wg.Wait()
}

// Parses a port range string in the form "start-end" and returns the start and end ports as integers
func parsePortRange(portRange string) (int, int) {
    ports := strings.Split(portRange, "-")
    start, err := strconv.Atoi(ports[0])
    if err != nil {
        fmt.Fprintf(os.Stderr, "Error parsing port range: %v\n", err)
        os.Exit(1)
    }
    end, err := strconv.Atoi(ports[1])
    if err != nil {
        fmt.Fprintf(os.Stderr, "Error parsing port range: %v\n", err)
        os.Exit(1)
    }
    return start, end
}

// Sends the specified number of file chunks to a given host and port using UDP
func sendFileChunks(host string, port int, file *os.File, numChunks int) {
    // Create the UDP address
    serverAddr, err := net.ResolveUDPAddr("udp", fmt.Sprintf("%s:%d", host, port))
    if err != nil {
        fmt.Fprintf(os.Stderr, "Error resolving server address: %v\n", err)
        return
    }

    // Open a UDP connection to the server
    conn, err := net.DialUDP("udp", nil, serverAddr)
    if err != nil {
        fmt.Fprintf(os.Stderr, "Error opening UDP connection: %v\n", err)
        return
    }
    defer conn.Close()

    // Read and send the specified number of file chunks
    for i := 0; i < numChunks; i++ {
        buf := make([]byte, 1024)