工作需要，经常会在工作的台式机和笔记本之间传文件或者需要拷贝文本，两个机器都位于局域网内，传文件或者文本的方式有很多种，之前是通过共享文件夹来进行文件的拷贝，或者通过SVN进行同步。文本传递比较简单，可以通过两台机器上装QQ登两个号码，或者在共享目录下建一个TXT，或者发电子邮件等等。

不过上面这些方法总觉得不直接，所以想基于P2P做一个小的局域网文件和文字传输小工具。

WinForm的工程，界面方面的代码就不贴了，大家自己根据喜好设计就好了，主要把TCP数据传输的代码和逻辑贴出来：

1. 文件和文本传输的通用方法：

private string ReceiveControl(Socket socket)
{
    int bufSize = 1024;
    byte[] buf = new byte[bufSize];
    int len = socket.Receive(buf);
    return len > 0 ? Encoding.UTF8.GetString(buf, 0, len) : String.Empty;
}
private void SendControl(Socket socket, string controlMsg)
{
    byte[] msgBytes = Encoding.UTF8.GetBytes(controlMsg);
    socket.Send(msgBytes);
}
private string ReceiveContent(Socket socket, int contentLen)
{
    int receivedLen = 0;
    int bufSize = 1024;
    byte[] buf = new byte[bufSize];
    StringBuilder sb = new StringBuilder();
    while (receivedLen < contentLen)
    {
        int len = socket.Receive(buf);
        if (len > 0)
        {
            sb.Append(Encoding.UTF8.GetString(buf, 0, len));
            receivedLen += len;
        }
    }
    return sb.ToString();
}
private void SendContent(Socket socket, string content)
{
    byte[] contentBytes = Encoding.UTF8.GetBytes(content);
    SendControl(socket, contentBytes.Length.ToString());
    ReceiveControl(socket);
    socket.Send(contentBytes);
}
private void ReceiveFile(Socket socket, string fileName, int fileLen)
{
    string filePath = Path.Combine(GetCurrentUserDesktopPath(), RenameConflictFileName(fileName));
    using (Stream fs = new FileStream(filePath, FileMode.Create, FileAccess.ReadWrite))
    {
        int bufLen = 1024;
        int receivedLen = 0;
        byte[] buf = new byte[bufLen];
        int len = 0;
        while (receivedLen < fileLen)
        {
            len = socket.Receive(buf);
            fs.Write(buf, 0, len);
            receivedLen += len;
        }
    }
}
private void SendFile(Socket socket, string filePath)
{
    using (Stream fs = new FileStream(filePath, FileMode.Open, FileAccess.Read))
    {
        SendControl(socket, GetFileNameFromPath(filePath));
        ReceiveControl(socket);
        SendControl(socket, fs.Length.ToString());
        ReceiveControl(socket);
        int bufLen = 1024;
        byte[] buf = new byte[bufLen];
        long readLen = 0;
        long fileLen = fs.Length;
        int len = 0;
        while (readLen < fileLen)
        {
            len = fs.Read(buf, 0, bufLen);
            readLen += len;
            int sentLen = 0;
            int realSent = 0;
            int left = 0;
            while (sentLen < len)
            {
                left = len - realSent;
                realSent = socket.Send(buf, sentLen, left, SocketFlags.None);
                sentLen += realSent;
            }
        }
    }
}

2.连接，发送文字/文件，重命名文件等方法：

private void SendText()
{
    if (connected)
    {
        if (!String.IsNullOrEmpty(this.TextToSend.Text))
        {
            string txt = this.TextToSend.Text;
            SendControl(clientSocket, "Text");
            ReceiveControl(clientSocket);
            SendContent(clientSocket, txt);
            ReceiveControl(clientSocket);
        }
    }
}
 
private void Connect()
{
    try
    {
        if (!connected)
        {
            passive = false;
            IPAddress serverIPAddress = IPAddress.Parse(this.ServerIPAddress.Text);
            clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            clientSocket.Connect(serverIPAddress, 60000);
            string msg = ReceiveControl(clientSocket);
            if (msg.Equals("Connected"))
            {
                this.ConnectBtn.Text = "Disconnect";
                connected = true;
            }
        }
        else
        {
            passive = true;
            SendControl(clientSocket, "Disconnect");
            clientSocket.Close();
            this.ConnectBtn.Text = "Connect";
            connected = false;
        }
    }
    catch (Exception err)
    {
        MessageBox.Show(string.Format("Failed to connect to server, error: {0}", err.ToString()));
    }
}
 
private void ServerThread()
{
    IPAddress local = IPAddress.Parse("0.0.0.0");
    Socket server = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
    server.Bind(new IPEndPoint(local, 60000));
    server.Listen(1);
    while (true)
    {
        Socket receivedClientSocket = server.Accept();
        IPEndPoint clientEndPoint = (IPEndPoint)receivedClientSocket.RemoteEndPoint;
        SendControl(receivedClientSocket, "Connected");
        if (passive)
        {
            clientSocket = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);
            clientSocket.Connect(clientEndPoint.Address, 60000);
            string msg = ReceiveControl(clientSocket);
            if (msg.Equals("Connected"))
            {
                connected = true;
                this.ConnectBtn.Text = "Disconnect";
                this.ServerIPAddress.Text = clientEndPoint.Address.ToString();
            }
        }
        while (connected)
        {
            string msg = ReceiveControl(receivedClientSocket);
            switch (msg)
            {
                case "Disconnect":
                    receivedClientSocket.Close();
                    clientSocket.Close();
                    this.ConnectBtn.Text = "Connect";
                    passive = true;
                    connected = false;
                    break;
                case "Text":
                    SendControl(receivedClientSocket, "Received");
                    int length = Convert.ToInt32(ReceiveControl(receivedClientSocket));
                    SendControl(receivedClientSocket, "Received");
                    string content = ReceiveContent(receivedClientSocket, length);
                    SendControl(receivedClientSocket, "Received");
                    this.TextToSend.Text = content;
                    break;
                case "File":
                    SendControl(receivedClientSocket, "Received");
                    string fileName = ReceiveControl(receivedClientSocket);
                    SendControl(receivedClientSocket, "Received");
                    int fileLen = Convert.ToInt32(ReceiveControl(receivedClientSocket));
                    SendControl(receivedClientSocket, "Received");
                    ReceiveFile(receivedClientSocket, fileName, fileLen);
                    SendControl(receivedClientSocket, "Received");
                    MessageBox.Show("File Received");
                    break;
            }
        }
    }
}
 
private string GetFileNameFromPath(string path)
{
    int index = path.LastIndexOf('\\');
    return path.Substring(index + 1);
}
 
private string RenameConflictFileName(string originalName)
{
    string desktopPath = GetCurrentUserDesktopPath();
    int extensionIndex = originalName.LastIndexOf(".");
    string fileName = originalName.Substring(0, extensionIndex);
    string extensionName = originalName.Substring(extensionIndex + 1);
 
    int renameIndex = 1;
    string newNameSuffix = String.Format("({0})", renameIndex);
    string finalName = originalName;
    string filePath = Path.Combine(desktopPath, finalName);
    if (File.Exists(filePath))
    {
        finalName = String.Format("{0} {1}.{2}", fileName, newNameSuffix, extensionName);
        filePath = Path.Combine(desktopPath, finalName);
    }
    while (File.Exists(filePath))
    {
        renameIndex += 1;
        string oldNameSuffix = newNameSuffix;
        newNameSuffix = String.Format("({0})", renameIndex);
        finalName = finalName.Replace(oldNameSuffix, newNameSuffix);
        filePath = Path.Combine(desktopPath, finalName);
    }
 
    return finalName;
}
 
private string GetCurrentUserDesktopPath()
{
    return Environment.GetFolderPath(System.Environment.SpecialFolder.Desktop);
}