Why does my file transfer over sockets result in an empty file?

File Transmission Over Sockets: Addressing Data Exchange Issues

In Java programming, sending and receiving files as byte arrays over sockets can encounter challenges. This guide aims to resolve an issue faced by a developer who observed an empty file creation during the data transfer process between client and server.

Server Configuration

The server's task is to receive data from the client. The following code snippet outlines the server's functionality:

<code class="java">byte[] bytes = new byte[1024];

in.read(bytes);
System.out.println(bytes);

FileOutputStream fos = new FileOutputStream("C:\test2.xml");
fos.write(bytes);</code>

The issue arises in the fos.write(bytes) line, where the bytes array contains incomplete data. This is because in.read(bytes) only reads a partial amount of data into the array.

Client Configuration

The client's duty is to send data to the server. However, the following code excerpt contains an incomplete action:

<code class="java">//out.write(bytes);
System.out.println(bytes);</code>

The line out.write(bytes) is commented out, preventing the data in the bytes array from being written to the server. Consequently, the server receives an empty array, resulting in the creation of an empty file.

Solution

To resolve this issue, the correct way to copy a stream in Java is to utilize a buffer and continuously read data into the buffer until there is no more data to read. The following code fragment illustrates this approach:

<code class="java">byte[] buffer = new byte[8192];
while ((count = in.read(buffer)) > 0) {
  out.write(buffer, 0, count);
}</code>

The above is the detailed content of Why does my file transfer over sockets result in an empty file?. For more information, please follow other related articles on the PHP Chinese website!