Develop Reference

HttpsUrlConnection response returned from servlet contains extra 'b''0''\r\n' characters when read through python library

I am using HttpsURLConnection to call a server and return the response returned from the HttpsURLConnection from my servlet. I am copying the response from HttpssURLConnection to HttpServletresponse using streams, copying bytes from the httpconnection response input stream to the response's output stream, checking the end by seeing if read returns < 0.
Following is the code for copying the response. The variable response is of type HttpServletResponse and the variable httpCon is of type HttpsURLConnection.
InputStream responseStream = httpCon.getInputStream();
if (responseStream != null)
{
OutputStream os = response.getOutputStream();
byte[] buffer = new byte[1024];
int len;
while ((len = responseStream.read(buffer)) >= 0)
{
os.write(buffer, 0, len);
}
os.flush();
os.close();
}
On the client side, I am using python requests library to read the response.
What I am seeing that if I use the curl to test my servlet, I am getting the proper response json, response = u'{"key":"value"}'.
If i read it from the requests python, it is putting some extra characters in the response , the response looks like the following
response = u'b0\r\n{"key":"value"}\r\n0\r\n\r\n'
Both the strings are unicode. But the second one has extra characters.
Same resonse if I try from curl/Postman restclient, I am able to get it properly. But from python requests, it is not working. I tried another livetest library in python, with that also, it is not working and the response has same characters. I also tried to change the accept-encoding header but it did not have any effect.
Because of this, I am not able to parse the json.
I don't want to change the client to parse this kind of string.
Can I change something on the server so that it will work correctly?

Did the response contain the below header "Transfer-Encoding: chunked"?
The response should be in Chunked transfer encoding
https://en.wikipedia.org/wiki/Chunked_transfer_encoding.
In this case, you get \r\n0\r\n\r\n at the end of the response is as expected since it is terminating symbol of this encoding. I guest curl/Postman just help us to handle Chunked transfer encoding, so you can't find these chunked symbols.

Java socket connection hangs 60 seconds before reading last line

I have developed manually a soap connection via Java sockets (it was a very simple soap request and Axis was giving lots of build problem).
To achieve this, I basically copied the HTTP header I was getting out of Soap UI when , and coded the follwing:
String hostname = "aaaaa";
int port = 11111;
InetAddress addr = InetAddress.getByName(hostname);
Socket sock = new Socket(addr, port);
sock.setSoTimeout(100000);
BufferedWriter wr = new BufferedWriter(new OutputStreamWriter(sock.getOutputStream(),"UTF-8"));
wr.write("POST " + "http://aaaa:11111/servicePath" + " HTTP/1.1\r\n");
wr.write("Host: aaaaa:11111\r\n");
wr.write("Accept-Encoding: gzip,deflate\r\n");
wr.write("Content-Length: " + soapXml.length() + "\r\n");
wr.write("Content-Type: text/xml; charset=\"UTF-8\"\r\n");
//wr.write("Connection: Keep-Alive\r\n");
wr.write("SOAPAction: \"/someSoapAction\"\r\n");
wr.write("User-Agent: Apache-HttpClient/4.1.1 (java 1.5)\r\n");
wr.write("\r\n");
wr.write(soapXml);
wr.flush();
The requests are successful, meaning I get from the service the responses I expect.
For instance, when I put in my hand written "soapXml" some invalid parameters, I get a 500 error back with XML explaining the problem, If I set everything correctly I get a 200 OK with an xml body following the header.
The problem is that the socket hangs 60 seconds before reading the HTTP body in case of a 200OK.
It basically reads the full header, then waits 60 seconds, then (I think some protocol times out and) finally reads the xml body.
Here's the code with which I read the response:
String line;
BufferedReader rd = new BufferedReader(new java.io.InputStreamReader(sock.getInputStream(),"UTF-8"));
while ((line = rd.readLine()) != null) {
i++;
LOG.debug("cycle: "+i+" -------- "+line);
//after printing the header, it hangs 60 seconds before printing the follwing XML
if ((line.length() >0) && (line.charAt(0) == '<'))
{
responseXML = line;
}
}
Here is a sample 200 OK header:
HTTP/1.1 200 OK
Server: Apache-Coyote/1.1
Content-Type: text/xml;charset=utf-8
Content-Length: 1052
Date: Sun, 13 Jan 2013 08:33:45 GMT -- hanging 60 seconds here
-- blank line
<?xml version="1.0" encoding="UTF-8"?>................</SOAP-ENV:Envelope>
Has anybody ever faced this? Please note this is not a server problem apparently, since with soap UI the answer is immediately provided.
Thank you

The server is keeping the connection open for HTTP keep-alive, clearly for a 60 second timeout. Either change to HTTP 1.0 or else take note of the returned Content-length header and stop reading at that many bytes.

The server environment change (a new machine was provided) solved the issue.
Now response time is below 1 sec also for 200OK.
Unluckily I don't have any details regarding the tech stack of the envrionment. Anyways thanks for help.

Tomcat - Servlet response blocking - problems with flush

I'm using Tomcat 6.0.36 and JRE 1.5.0, and I'm doing development work on Windows 7.
As a proof of concept for some work I'm doing, from Java code I'm HTTP posting some XML over a socket to a servlet. The
servlet then echos back the xml. In my first implementation, I was handing the input stream at both ends to an XML
document factory to extract the xml that was sent over the wire. This worked without a hitch in the servlet but failed
on the client side. It turned out that it failed on the client side because the reading of the response was blocking
to the point that the document factory was timing out and throwing an exception prior to the entire response arriving.
(The behaviour of the document factory is now moot because, as I describe below, I am getting the same blocking issue
without the use of the document factory.)
To try to work through this blocking issue, I then came up with a simpler version of the client side code and the
servlet. In this simpler version, I eliminated the document builder from the equation. The code on both sides now
simply reads the text from their respective input streams.
Unfortunately, I still have this blocking issue with the response and, as I describe below, it has not been resolved by
simply calling response.flushBuffer(). Google searches retrieved only one relevant topic that I could find
(Tomcat does not flush the response buffer) but this was not the exact same
issue.
I have included my code and explained the exact issues below.
Here's my servlet code (remember, this is bare-bones proof-of-concept code, not production code),
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import javax.servlet.ServletConfig;
import javax.servlet.ServletException;
import javax.servlet.http.HttpServlet;
import javax.servlet.http.HttpServletRequest;
import javax.servlet.http.HttpServletResponse;
public final class EchoXmlServlet extends HttpServlet {
public void init(ServletConfig config) throws ServletException {
System.out.println("EchoXmlServlet loaded.");
}
public void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException {
}
public void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException {
try {
processRequest(request, response);
}
catch(Exception e) {
e.printStackTrace();
throw new ServletException(e);
}
System.out.println("Response sent.");
return;
}
private final void processRequest(HttpServletRequest request, final HttpServletResponse response) throws Exception {
String line = null;
StringBuilder sb = new StringBuilder();
LineNumberReader lineReader = new LineNumberReader(new InputStreamReader(request.getInputStream(), "UTF-8"));
while((line = lineReader.readLine()) != null) {
System.out.println("line: " + line);
sb.append(line);
sb.append("\n");
}
sb.append("An additional line to see when it turns up on the client.");
System.out.println(sb);
response.setHeader("Content-Type", "text/xml;charset=UTF-8");
response.getOutputStream().write(sb.toString().getBytes("UTF-8"));
// Some things that were tried.
//response.getOutputStream().print(sb.toString());
//response.getOutputStream().print("\r\n");
//response.getOutputStream().flush();
//response.flushBuffer();
}
public void destroy() {
}
}
Here's my client side code,
import java.io.BufferedOutputStream;
import java.io.InputStreamReader;
import java.io.LineNumberReader;
import java.io.OutputStream;
import java.net.Socket;
public final class SimpleSender {
private String host;
private String path;
private int port;
public SimpleSender(String host, String path, int port) {
this.host = host;
this.path = path;
this.port = port;
}
public void execute() {
Socket connection = null;
String line;
try {
byte[] xmlBytes = getXmlBytes();
byte[] headerBytes = getHeaderBytes(xmlBytes.length);
connection = new Socket(this.host, this.port);
OutputStream outputStream = new BufferedOutputStream(connection.getOutputStream());
outputStream.write(headerBytes);
outputStream.write(xmlBytes);
outputStream.flush();
LineNumberReader lineReader
= new LineNumberReader(new InputStreamReader(connection.getInputStream(), "UTF-8"));
while((line = lineReader.readLine()) != null) {
System.out.println("line: " + line);
}
System.out.println("The response is read.");
}
catch(Exception e) {
e.printStackTrace();
}
finally {
try {
connection.close();
}
catch(Exception e) {}
}
}
private byte[] getXmlBytes() throws Exception {
StringBuffer sb = null;
sb = new StringBuffer()
.append("<my-xml>\n")
.append("Hello to myself.\n")
.append("</my-xml>\n");
return sb.toString().getBytes("UTF-8");
}
private byte[] getHeaderBytes(int contentLength) throws Exception {
StringBuffer sb = null;
sb = new StringBuffer()
.append("POST ")
.append(this.path)
.append(" HTTP/1.1\r\n")
.append("Host: ")
.append(this.host)
.append("\r\n")
.append("Content-Type: text/xml;charset=UTF-8\r\n")
.append("Content-Length: ")
.append(contentLength)
.append("\r\n")
.append("\r\n");
return sb.toString().getBytes("UTF-8");
}
}
When a request is sent to the servlet via a call to SimpleSender.execute(), the code in the servlet that receives the
request reads the xml without a hitch. My servlet code also exits from its processRequest() and doPost() without a
hitch. This is the immediate (i.e. there is no blocking between any output line) output on the server:
line: <my-xml>
line: Hello to myself.
line: </my-xml>
<my-xml>
Hello to myself.
</my-xml>
An additional line to see when it turns up on the client.
Response sent.
The output above is exactly as expected.
On the client side, however, the code outputs the following then blocks:
HELLO FROM MAIN
line: HTTP/1.1 200 OK
line: Server: Apache-Coyote/1.1
line: Content-Type: text/xml;charset=UTF-8
line: Content-Length: 74
line: Date: Sun, 18 Nov 2012 23:58:43 GMT
line:
line: <my-xml>
line: Hello to myself.
line: </my-xml>
After about 20 seconds of blocking (I timed it), the following lines are output on the client side,
line: An additional line to see when it turns up on the client.
The response is read.
GOODBYE FROM MAIN
Note that the entire output on the server side is fully visible while the blocking is occurring on the client side.
From there, I tried to flush on the server side to try to fix this issue. I independently tried two methods of flushing:
response.flushBuffer() and response.getOutputStream().flush(). With both methods of flushing, I still had blocking on
the client side (but in a different part of the response), but I had other issues as well. Here's where the client
blocked,
HELLO FROM MAIN
line: HTTP/1.1 200 OK
line: Server: Apache-Coyote/1.1
line: Content-Type: text/xml;charset=UTF-8
line: Transfer-Encoding: chunked
line: Date: Mon, 19 Nov 2012 00:21:53 GMT
line:
line: 4a
line: <my-xml>
line: Hello to myself.
line: </my-xml>
line: An additional line to see when it turns up on the client.
line: 0
line:
After blocking for about 20 seconds, the following is output on the client side,
The response is read.
GOODBYE FROM MAIN
There are three problems with this output on the client side. Firstly, the reading of the response is still blocking, it's
just blocking after a different part of the response. Secondly, I have unanticipated characters returned ("4a", "0").
Finally, the headers have changed. I've lost the Content-Length header, and I have gained the
"Transfer-encoding: chunked" header.
So, without a flush, my response is blocking prior to sending the final line and a termination to the response. However,
with a flush, the response is still blocking but now I'm getting characters I don't want and a change to the headers I
don't want.
In Tomcat, my connector has the default definition,
<Connector port="8080" protocol="HTTP/1.1" connectionTimeout="20000" redirectPort="8443" />
The connectionTimeout is set for 20 seconds. When I changed this to 10 seconds, my client side code blocked for 10
seconds instead of 20. So it appears that it is the connection timeout, as managed by Tomcat, that is causing my
response to be fully flushed and terminated.
Is there something additional I should be doing in my servlet code to indicate that my response is finished?
Has anyone got suggestions as to why my response is blocking prior to sending the final line and termination indicator?
Has anyone got suggestions as to why flush is sending unwanted characters and why the response is still blocking after
a flush?
If someone has the time, could you tell me if you get the same issues if you try running the code included in this post?
EDIT - In response to Guido's first reply
Guido,
Thanks very much for your reply.
Your client is blocking because you are using readLine to read the
body of the message. readLine hangs because the body does not end with
a line feed
No, I don't think this is true. Firstly, in my original version of my code, I was not using line readers on either the client or server side. On both sides, I was handing the stream to the xml document factory and letting it read from the stream. On the server, this worked fine. On the client, it timed out. (On the client, I was reading to the end of the headers prior to passing the stream to the document factory.)
Secondly, when I change my client code to not use a line reader, the blocking still occurs. Here's a version of SimpleSender.execute() that does not use a line reader,
public void execute() {
Socket connection = null;
int byteCount = 0;
try {
byte[] xmlBytes = getXmlBytes();
byte[] headerBytes = getHeaderBytes(xmlBytes.length);
connection = new Socket(this.host, this.port);
OutputStream outputStream = new BufferedOutputStream(connection.getOutputStream());
outputStream.write(headerBytes);
outputStream.write(xmlBytes);
outputStream.flush();
while(connection.getInputStream().read(new byte[1]) >= 0) {
++byteCount;
}
System.out.println("The response is read: " + byteCount);
}
catch(Exception e) {
e.printStackTrace();
}
finally {
try {
connection.close();
}
catch(Exception e) {}
}
return;
}
The above code blocks at,
HELLO FROM MAIN
then 20 seconds later, finishes wtih,
The response is read: 235
GOODBYE FROM MAIN
I think the above shows conclusively the problem is not with the use of a line reader on the client side.
sb.append("An additional line to see when it turns up on the client.\n");
The addition of the return in the above line just defers the block to one line later. I had tested this prior to my OP and I just tested again.
If you want to do your own HTTP parser, you have to read through the headers until you get two blank lines.
Yes, I do know that, but in this contrived simple example, it is a moot point. On the client, I am simply outputting the returned HTTP message, headers and all.
Then you need to scan the headers to see if you had a Content-Length header. If there is no Content-Length then you are done. If there is a Content-Length you need to parse it for the length, then read exactly that number of additional bytes from the stream. This allows HTTP to transport both text data and also binary data which has no line feeds.
Yup, all true but not relevant in this contrived simple example.
I recommend you replace the guts of your client code HTTP writer/parse with a pre-written client library that handles these details for you.
I agree entirely. I was actually hoping to pass off the handling of the streams to the xml document factories. As a way of dealing with my blocking issues, I also looked into Apache commons-httpclient. The new version (httpcomponents) still leaves it to the developer to handle the stream of a post return (from what I can tell), so that was of no use. If you can suggest another library, I'd be interested for sure.
I've disagreed with your points but I thank you for your reply and I mean no offense or any negative intimations by my disagreement. I'm obviously doing something wrong or not doing something I should, but I don't think the line reader is the issue. Additionally, where are those funky characters coming from if I flush? Why does the blocking occur when a line reader is not in use on the client side?
Also, I have replicated the issue on Jetty. Hence, this is definetly not a Tomcat issue and very much a 'me' issue. I'm doing something wrong but I don't know what it is.

Your server code looks fine. The problem is with your client code. It does not obey the HTTP protocol and is treating the response like a bunch of lines.
Quick fix on the server. Change to:
sb.append("An additional line to see when it turns up on the client.\n");
Your client is blocking because you are using readLine to read the body of the message. readLine hangs because the body does not end with a line feed. Finally Tomcat times out, closes the connection, your buffered reader detects this and returns the remaining data.
If you make the change above (to the server), This will make your client appear to work as you expect. Even though it is still wrong.
If you want to do your own HTTP parser, you have to read through the headers until you get two blank lines. Then you need to scan the headers to see if you had a Content-Length header. If there is no Content-Length then you are done. If there is a Content-Length you need to parse it for the length, then read exactly that number of additional bytes from the stream. This allows HTTP to transport both text data and also binary data which has no line feeds.
I recommend you replace the guts of your client code HTTP writer/parse with a pre-written client library that handles these details for you.

LOL Ok, I was doing something wrong (by omission). The solution to my issue? Add the following header to my http request,
Connection: close
That simple. Without that, the connection was staying alive. My code was relying on the server signifying that it was finished, but, the server was still listening on the open connection rather than closing it.
The header causes the server to close the connection when it finishes writing the response (which I guess is signified when its call to doPost(...) returns).
Addendum
With regard to the funky characters when flush() is called...
My server code, now that I'm using Connection: close, does not call flush(). However, if the content to be sent back is large enough (larger than the Tomcat connector's buffer size I suspect), I still get the funky characters sent back and the header 'Transfer-Encoding: chunked' appears in the response.
To fix this, I explicitly call, on the server side, response.setContentLength(...) prior to writing my response. When I do this, the Content-Length header is in the response instead of Transfer-Encoding: chunked, and I don't get the funky characters.
I'm not willing to burn any more time on this as my code is now working, but I do wonder if the funky characters were chunk delimiters, where, once I explicitly set the content length, the chunk delimiters were no longer necessary.

Http Post not posting data

I'm trying to post some data from a Java client using sockets. It talks to localhost running php code, that simply spits out the post params sent to it.
Here is Java Client:
public static void main(String[] args) throws Exception {
Socket socket = new Socket("localhost", 8888);
String reqStr = "testString";
String urlParameters = URLEncoder.encode("myparam="+reqStr, "UTF-8");
System.out.println("Params: " + urlParameters);
try {
Writer out = new OutputStreamWriter(socket.getOutputStream(), "UTF-8");
out.write("POST /post3.php HTTP/1.1\r\n");
out.write("Host: localhost:8888\r\n");
out.write("Content-Length: " + Integer.toString(urlParameters.getBytes().length) + "\r\n");
out.write("Content-Type: text/html\r\n\n");
out.write(urlParameters);
out.write("\r\n");
out.flush();
InputStream inputstream = socket.getInputStream();
InputStreamReader inputstreamreader = new InputStreamReader(inputstream);
BufferedReader bufferedreader = new BufferedReader(inputstreamreader);
String string = null;
while ((string = bufferedreader.readLine()) != null) {
System.out.println("Received " + string);
}
} catch(Exception e) {
e.printStackTrace();
} finally {
socket.close();
}
}
This is how post3.php looks like:
<?php
$post = $_REQUEST;
echo print_r($post, true);
?>
I expect to see an array (myparams => "testString") as the response. But its not passing post args to server.
Here is output:
Received HTTP/1.1 200 OK
Received Date: Thu, 25 Aug 2011 20:25:56 GMT
Received Server: Apache/2.2.17 (Unix) mod_ssl/2.2.17 OpenSSL/0.9.8r DAV/2 PHP/5.3.6
Received X-Powered-By: PHP/5.3.6
Received Content-Length: 10
Received Content-Type: text/html
Received
Received Array
Received (
Received )
Just a FYI, this setup works for GET requests.
Any idea whats going on here?

As Jochen and chesles rightly point out, you are using the wrong Content-Type: header - it should indeed be application/x-www-form-urlencoded. However there are several other issues as well...
The last header should be seperated from the body by a blank line between the headers and the body. This should be a complete CRLF (\r\n), in your code it is just a new line (\n). This is an outright protocol violation and I'm a little surprised you haven't just got a 400 Bad Request back from the server, although Apache can be quite forgiving in this respect.
You should specify Connection: close to ensure that you are not left hanging around with open sockets, the server will close the connection as soon as the request is complete.
The final CRLF sequence is not required. PHP is intelligent enough to sort this out by itself, but other server languages and implementations may not be...
If you are working with any standardised protocol in it's raw state, you should always start by at least scanning over the RFC.
Also, please learn to secure your Apache installs...

It looks like you are trying to send data in application/x-www-form-urlencoded format, but you are setting the Content-Type to text/html.

Use
out.write("Content-Type: application/x-www-form-urlencoded\n\n");
instead. As this page states:
The Content-Length and Content-Type headers are critical because they tell the web server how many bytes of data to expect, and what kind, identified by a MIME type.
For sending form data, i.e. data in the format key=value&key2=value2 use application/x-www-form-urlencoded. It doesn't matter if the value contains HTML, XML, or other data; the server will interpret it for you and you'll be able to retrieve the data as usual in the $_POST or $_REQUEST arrays on the PHP end.
Alternatively, you can send your data as raw HTML, XML, etc. using the appropriate Content-Type header, but you then have to retrieve the data manually in PHP by reading the special file php://input:
<?php
echo file_get_contents("php://input");
?>
As an aside, if you're using this for anything sufficiently complex, I would strongly recommend the use of an HTTP client library like HTTPClient.

How can I send an HTTP Response using only standard network libraries?

I'm working on my first homework project in a web programming class, which is to write a simple web server in Java. I'm at the point where I have data being transmitted back and forth, and to the untrained eye, my baby server seems to be working fine. However, I can't find a way to send appropriate responses. (In other words, an invalid page request would show a 404-ish HTML page, but it still returns a 200 OK status when I view response headers).
I'm limited to being able to use standard network libraries for socket management and standard I/O libraries to read and write bytes and strings from an input stream. Here's some pertinent code:
From my main...
ServerSocket servSocket = new ServerSocket(port, 10); // Bind the socket to the port
System.out.println("Opened port " + port + " successfully!");
while(true) {
//Accept the incoming socket, which means that the server process will
//wait until the client connects, then prepare to handle client commands
Socket newDataSocket = servSocket.accept();
System.out.println("Client socket created and connected to server socket...");
handleClient(newDataSocket); //Call handleClient method
}
From the handleClient method...(inside a loop that parses the request method and path)
if(checkURL.compareTo("/status") == 0) { // Check to see if status page has been requested
System.out.println("STATUS PAGE"); // TEMPORARY. JUST TO MAKE SURE WE ARE PROPERLY ACCESSING STATUS PAGE
sendFile("/status.html", dataStream);
}
else {
sendFile(checkURL, dataStream); // If not status, just try the input as a file name
}
From sendFile method...
File f = new File(where); // Create the file object
if(f.exists() == true) { // Test if the file even exists so we can handle a 404 if not.
DataInputStream din;
try {
din = new DataInputStream(new FileInputStream(f));
int len = (int) f.length(); // Gets length of file in bytes
byte[] buf = new byte[len];
din.readFully(buf);
writer.write("HTTP/1.1 200 OK\r\n"); // Return status code for OK (200)
writer.write("Content-Length: " + len + "\r\n"); // WAS WRITING TO THE WRONG STREAM BEFORE!
writer.write("Content-Type: "+type+"\r\n\r\n\r\n"); // TODO VERIFY NEW CONTENT-TYPE CODE
out.write(buf); // Writes the FILE contents to the client
out.flush();
out.close();
} catch (FileNotFoundException e) {
e.printStackTrace(); // Not really handled since that's not part of project spec, strictly for debug.
}
}
else {
writer.write("HTTP/1.1 404 Not Found\r\n"); // Attempting to handle 404 as simple as possible.
writer.write("Content-Type: text/html\r\n\r\n\r\n");
sendFile("/404.html", sock);
}
Can anybody explain how, in the conditional from sendFile, I can change the response in the 404 block (Like I said before, the response headers still show 200 OK)? This is bugging the crap out of me, and I just want to use the HTTPResponse class but I can't. (Also, content length and type aren't displayed if f.exists == true.)
Thanks!

Edit It looks to me like in the 404 situation, you're sending something like this:
HTTP/1.1 404 Not Found
Content-Type: text/html
HTTP/1.1 200 OK
Content-Length: 1234
Content-Type: text/html
...followed by the 404 page. Note the 200 line following the 404. This is because your 404 handling is calling sendFile, which is outputting the 200 response status code. This is probably confusing the receiver.
Old answer that missed that:
An HTTP response starts with a status line followed (optionally) by a series of headers, and then (optionally) includes a response body. The status line and headers are just lines in a defined format, like (to pick a random example):
HTTP/1.0 404 Not Found
To implement your small HTTP server, I'd recommend having a read through the spec and seeing what the responses should look like. It's a bit of a conceptual leap, but they really are just lines of text returned according to an agreed format. (Well, it was a conceptual leap for me some years back, anyway. I was used to environments that over-complicated things.)
It can also be helpful to do things like this from your favorite command line:
telnet www.google.com 80
GET /thispagewontbefound
...and press Enter. You'll get something like this:
HTTP/1.0 404 Not Found
Content-Type: text/html; charset=UTF-8
X-Content-Type-Options: nosniff
Date: Sun, 12 Sep 2010 23:01:14 GMT
Server: sffe
Content-Length: 1361
X-XSS-Protection: 1; mode=block
...followed by some HTML to provide a friendly 404 page. The first line above is the status line, the rest are headers. There's a blank line between the status line/headers and the first line of content (e.g., the page).

The problem you are seeing is most likely related to a missing flush() on your writer. Depending on which type of Writer you use the bytes are first written to a buffer that needs to be flushed to the stream. This would explain why Content-Length and Content-Type are missing in the output. Just flush it before you write additional data to the stream.
Further you call sendFile("/404.html", sock);. You did not post the full method here - but I suppose that you call it recursively inside sendFile and thus send the 200 OK status for your file /404.html.

Based on your reported symptoms, I think the real problem is that you are not actually talking to your server at all! The evidence is that 1) you cannot get a 404 response, and 2) a 200 response does not have the content length and type. Neither of these should be possible ... if you are really talking to the code listed above.
Maybe:
you are talking to an older version of your code; i.e. something is going wrong in your build / deploy cycle,
you are (mistakenly) trying to deploy / run your code in a web container (Jetty, Tomcat, etc), or
your client code / browser is actually talking to a different server due to proxying, an incorrect URL, or something like that.
I suggest that you add some trace printing / logging at appropriate points of your code to confirm that it is actually being invoked.