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Editorial Team
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Asked: 2026-05-30T06:17:29+00:00

I’m running into trouble with this basic, unsophisticated Web Server I wrote in Java.

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I’m running into trouble with this basic, unsophisticated Web Server I wrote in Java. For some reason, instead of sending the “200 OK” or “404 Not Found” solely to the browser, they’re written onto whatever file is being retrieved. For example, if I try to get an index.html file, I am returned:

example

….rather than the browser trying to compile the HTML.
It’s even worse when trying to get an image, as the file becomes corrupt from the server trying to append the “200 OK” & Content-type to it. Can anyone offer any insight as to how to send the status line & content-type separate from the actual HTML/JPG file? The error goes away entirely when I comment out the “os.writeBytes(statusLine)”, etc, but I still want to send these messages to the browser…just not merged with the file. Any help would be greatly appreciated.

import java.io.*;
import java.net.*;
import java.util.*;

final class HttpRequest implements Runnable {
    final static String CRLF = "\r\n";
    Socket socket;

    // Constructor
    public HttpRequest(Socket socket) throws Exception {
        this.socket = socket;
    }

    // Implement the run() method of the Runnable interface.
    public void run() {
        try {
            processRequest();
        } catch (Exception e) {
            System.out.println(e);
        }
    }

    private static void sendBytes(FileInputStream fis, OutputStream os) 
    throws Exception {
    // Construct a 1K buffer to hold bytes on their way to the socket.
    byte[] buffer = new byte[1024];
    int bytes = 0;

    // Copy requested file into the socket's output stream.
    while((bytes = fis.read(buffer)) != -1 ) {
        os.write(buffer, 0, bytes);
        }
    }

    private static String contentType(String fileName) {
    if(fileName.endsWith(".htm") || fileName.endsWith(".html")) {
        return "text/html";
    }
    if(fileName.endsWith(".jpeg") || fileName.endsWith(".jpg")) {
    return "image/jpeg";
    }
    if(fileName.endsWith(".gif")) {
    return "image/gif";
    }
    return "application/octet-stream";
    }

    private void processRequest() throws Exception {
        // Get a reference to the socket's input and output streams.
        InputStream is = socket.getInputStream();
        DataOutputStream os = new DataOutputStream(socket.getOutputStream());

        // Set up input stream filters.
        BufferedReader br = new BufferedReader(new InputStreamReader(is));

        // Get the request line of the HTTP request message.
        String requestLine = new String(br.readLine());

        // Display the request line.
        System.out.println();
        System.out.println(requestLine);

        // Get and display the header lines.
        String headerLine = null;
        while ((headerLine = br.readLine()).length() != 0) {
            System.out.println(headerLine);
        }

    // Extract the filename from the request line.
    StringTokenizer tokens = new StringTokenizer(requestLine);
    tokens.nextToken(); // skip over the method, which should be "GET"
    String fileName = tokens.nextToken();
    // Prepend a "." so that file request is within the current directory.
    fileName = "." + fileName;

    // Open the requested file.
    FileInputStream fis = null;
    boolean fileExists = true;
    try {
    fis = new FileInputStream(fileName);
    } catch (FileNotFoundException e) {
    fileExists = false;
    }

    // Construct the response message.
    String statusLine = null;
    String contentTypeLine = null;
    String entityBody = null;
    if (fileExists) {
    statusLine = "200 OK" + CRLF;
    contentTypeLine = "Content-type: " + 
        contentType( fileName ) + CRLF;
    } else {
    statusLine = "404 NOT FOUND" + CRLF;
    contentTypeLine = "Content Not Found!" + CRLF;
    entityBody = "<HTML>" + 
        "<HEAD><TITLE>Not Found</TITLE></HEAD>" +
        "<BODY>Not Found</BODY></HTML>";
    }

    // Send the status line.
    os.writeBytes(statusLine);

    // Send the content type line.
    os.writeBytes(contentTypeLine);

    // Send a blank line to indicate the end of the header lines.
    os.writeBytes(CRLF);

    // Send the entity body.
    if (fileExists) {
    sendBytes(fis, os);
    fis.close();
    } else {
    os.writeBytes("File DNE: Content Not Found!");
    }

        // Close streams and socket.
        os.close();
        br.close();
        socket.close();
    }
    public static void main(String[] args) throws Exception {
        final ServerSocket ss = new ServerSocket(6789);
        while (true)
            new HttpRequest(ss.accept()).run();
    }
}
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1 Answer

  1. Editorial Team

    I believe you are missing a CRLF. Isn’t there an extra one needed, at the end of status line

    200 OK
    Content-Type: xxxx

    OF course you could read the HTTP spec, or do a wireshark trace 🙂

    Update: Yes, you have a lot of issues. Read Easy Http for a simple
    summary.

    But anyway you need to say “HTTP/1.0 200 OK” for example

    http://www.somehost.com/path/file.html

    first open a socket to the host http://www.somehost.com, port 80 (use the default port of 80 because none is specified in the URL). Then, send something like the following through the socket:

    GET /path/file.html HTTP/1.0
From: someuser@jmarshall.com
User-Agent: HTTPTool/1.0
[blank line here]

    The server should respond with something like the following, sent back through the same socket:

    HTTP/1.0 200 OK
Date: Fri, 31 Dec 1999 23:59:59 GMT
Content-Type: text/html
Content-Length: 1354

<html>
<body>
<h1>Happy New Millennium!</h1>
(more file contents)
  .
  .
  .
</body>
</html>
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