problem with file sending program in c#.

Question

hello,i am developing the file sending program in c#.

but the facing errors

Error from client side -> the sending parameter is null

Error from server side -> the listener problem.

Server SIDE CODE

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.Net.Sockets;
using System.IO;
using System.Net;
namespace isend
{
    public partial class receiver : Form
    {
        string inforeceiver;
        byte[] b1;
        string filesize;
        int m;

         IPAddress localAddr = IPAddress.Parse("192.168.1.16");
        public receiver()
        {
            InitializeComponent();
        }


        private void button1_Click(object sender, EventArgs e)
        {
            if (folderBrowserDialog1.ShowDialog() == DialogResult.OK)
            {
                textBox1.Text = folderBrowserDialog1.SelectedPath;
                TcpListener listen = new TcpListener(localAddr, 7);
                listen.Start();
                TcpClient client = listen.AcceptTcpClient();
                Stream s = client.GetStream();
                b1 = new byte[m];
                s.Read(b1, 0, b1.Length);
                File.WriteAllBytes(textBox1.Text + "\\" + inforeceiver.Substring(0, inforeceiver.LastIndexOf('.')),
                b1);
                listen.Stop();
                client.Close();
            }
        }

        private void Form3_Load_1(object sender, EventArgs e)
        {
            TcpListener listen = null;
            try
            {
                listen = new TcpListener(localAddr, 7);
                listen.Start();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.ToString());
            }
            try
            {
                TcpClient client = null;
                client = listen.AcceptTcpClient();
                MessageBox.Show("Client trying to connect");
                StreamReader sr = new StreamReader(client.GetStream());
                inforeceiver = sr.ReadLine();
                filesize = inforeceiver.Substring(inforeceiver.LastIndexOf('.') + 1);
                m = int.Parse(filesize);
                listen.Stop();
                client.Close();
            }
            catch (Exception ex)
            {
                MessageBox.Show(ex.Message);
            }
            }
        }

    }

CLient SIDE CODE

using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Linq;
using System.Text;
using System.Windows.Forms;
using System.IO;
using System.Net.Sockets;
using System.Net;

namespace isend
{
    public partial class sender : Form
    {
        string fileinfo;
        Byte[] b;
        OpenFileDialog op;
         string Server;
        public sender()
        {
            InitializeComponent();
        }

        private void button1_Click(object sender, EventArgs e)
        {
            op = new OpenFileDialog();
            if (op.ShowDialog() == DialogResult.OK)
            {
                string t = textBox1.Text = op.FileName;
                FileInfo finfo = new FileInfo(textBox1.Text);
                fileinfo = finfo.Name + "." + finfo.Length;
                label1.Text = fileinfo;
                try
                {
                    TcpClient client = new TcpClient(Server, 7);
                    StreamWriter sw = new StreamWriter(client.GetStream());
                    sw.WriteLine(fileinfo);
                    sw.Flush();
                }
                catch (Exception ex)
                {
                    MessageBox.Show(ex.Message);
                }
            }
}

private void button2_Click(object sender, EventArgs e)
{
    try
    {
        TcpClient client = new TcpClient(Server, 7);
        NetworkStream s = client.GetStream();
        b = File.ReadAllBytes(op.FileName);
        s.Write(b, 0, b.Length);
        client.Close();
    }
    catch (Exception ex)
    {
        MessageBox.Show(ex.Message);
    }
}

private void button3_Click(object sender, EventArgs e)
{
    Server = textBox2.Text;
}
}
}

Answer 1

Receiver Problem

I found that the receiver port was bad.  You used port 7 which is for ECHO messages which is UDP and you are using TCP.  You have to use a TCP port number.  See this webpage for list of common port numbers.  I rfecommend using a port number over 10,000 which isn't reserved and can be used for any protocol.

Send Problem

The Server string wasn't initialized in either button 1 or button 2.

fix this line : string Server;

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jdweng