如何用Java实现服务端文件传输 Java Socket传输文件示例

// 简化的服务端代码示例
ServerSocket serverSocket = new ServerSocket(12345); // 端口号
Socket socket = serverSocket.accept();

InputStream in = socket.getInputStream();
OutputStream out = new FileOutputStream("received_file.txt");

byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = in.read(buffer)) != -1) {
    out.write(buffer, 0, bytesRead);
}

out.close();
in.close();
socket.close();
serverSocket.close();

// 客户端断点续传示例（简化）
File file = new File("large_file.txt");
long fileSize = file.length();
long offset = 0; // 初始偏移量

// 检查本地是否有已传输的部分
File tempFile = new File("large_file.txt.tmp");
if (tempFile.exists()) {
    offset = tempFile.length();
}

Socket socket = new Socket("localhost", 12345);
DataOutputStream dos = new DataOutputStream(socket.getOutputStream());
DataInputStream dis = new DataInputStream(socket.getInputStream());

// 告知服务端文件大小和偏移量
dos.writeLong(fileSize);
dos.writeLong(offset);
dos.flush();

RandomAccessFile raf = new RandomAccessFile(file, "r");
raf.seek(offset);

byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = raf.read(buffer)) != -1) {
    dos.write(buffer, 0, bytesRead);
    offset += bytesRead;

    // 写入临时文件，保存进度
    FileOutputStream tempOut = new FileOutputStream(tempFile, true);
    tempOut.write(buffer, 0, bytesRead);
    tempOut.close();
}

raf.close();
dos.close();
socket.close();

// 使用NIO进行文件传输（简化）
FileInputStream fis = new FileInputStream("large_file.txt");
FileChannel inputChannel = fis.getChannel();

SocketChannel socketChannel = SocketChannel.open(new InetSocketAddress("localhost", 12345));

ByteBuffer buffer = ByteBuffer.allocate(4096);

while (inputChannel.read(buffer) > 0) {
    buffer.flip();
    socketChannel.write(buffer);
    buffer.clear();
}

inputChannel.close();
socketChannel.close();
fis.close();

// 使用SSL进行安全文件传输（简化）
SSLContext sslContext = SSLContext.getInstance("TLS");
sslContext.init(null, null, new SecureRandom());

SSLServerSocketFactory sslServerSocketFactory = sslContext.getServerSocketFactory();
SSLServerSocket sslServerSocket = (SSLServerSocket) sslServerSocketFactory.createServerSocket(12345);

SSLSocket sslSocket = (SSLSocket) sslServerSocket.accept();

InputStream in = sslSocket.getInputStream();
OutputStream out = new FileOutputStream("received_file.txt");

byte[] buffer = new byte[4096];
int bytesRead;
while ((bytesRead = in.read(buffer)) != -1) {
    out.write(buffer, 0, bytesRead);
}

out.close();
in.close();
sslSocket.close();
sslServerSocket.close();