使用SOCKET的Java Server通过同一台计算机上的浏览器将文件上传下载到其中

Question

I have a java server using sockets. I have an html file which contains a form that can be used to upload a file and send it. How can the server download that file without blocking. The browser never closes the connection and it just hangs in there I have beeping using readLine() from the input stream but it blocks. is there any way around this?

I appreciate any help here. Thanks

Answer 1

please clarify your requirement, it seems total chaos in your steps. 1. did your program run as client side or server side? 2. could you show your code? and show what blocked you? 3. It is much better if you can draw a working-flow of your program .

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Thanks for your supplement, do you want to upload a files through HTTP(writing in socket way). For this requirement, you could check the link link for how HTTP works [RFC 1867] ( https://tools.ietf.org/html/rfc1867 )

Below is the package of how socket way do: Suppose the server supplies the following HTML:

 <FORM ACTION="http://server.dom/cgi/handle"
       ENCTYPE="multipart/form-data"
       METHOD=POST>
 What is your name? <INPUT TYPE=TEXT NAME=submitter>
 What files are you sending? <INPUT TYPE=FILE NAME=pics>
 </FORM>

and the user types "Joe Blow" in the name field, and selects a text file "file1.txt" for the answer to 'What files are you sending?'

The client might send back the following data:

    Content-type: multipart/form-data, boundary=AaB03x

    --AaB03x
    content-disposition: form-data; name="field1"

    Joe Blow
    --AaB03x
    content-disposition: form-data; name="pics"; filename="file1.txt"
    Content-Type: text/plain

     ... contents of file1.txt ...
    --AaB03x--

If the user also indicated an image file "file2.gif" for the answer to 'What files are you sending?', the client might client might send back the following data:

    Content-type: multipart/form-data, boundary=AaB03x

    --AaB03x
    content-disposition: form-data; name="field1"

    Joe Blow
    --AaB03x
    content-disposition: form-data; name="pics"
    Content-type: multipart/mixed, boundary=BbC04y

    --BbC04y
    Content-disposition: attachment; filename="file1.txt"

Nebel & Masinter Experimental [Page 9]

RFC 1867 Form-based File Upload in HTML November 1995

    Content-Type: text/plain

    ... contents of file1.txt ...
    --BbC04y
    Content-disposition: attachment; filename="file2.gif"
    Content-type: image/gif
    Content-Transfer-Encoding: binary

      ...contents of file2.gif...
    --BbC04y--
    --AaB03x--

Answer 2

I have server running on port. I want it to gather the data sent by a POST request which carries a file (Not just text but png image). for example here is a server:

public void run() {
    try {
        InputStream is = insocket.getInputStream();
        PrintWriter out = new PrintWriter(insocket.getOutputStream());
        BufferedReader in = new BufferedReader(new InputStreamReader(is));
        String line;
        line = in.readLine();
        String request_method = line;
        System.out.println("HTTP-HEADER: " + line);
        line = "";
        // looks for post data
        int postDataI = -1;
        while ((line = in.readLine()) != null && (line.length() != 0)) {
            System.out.println("HTTP-HEADER: " + line);
            if (line.indexOf("Content-Length:") > -1) {
                postDataI = new Integer(
                        line.substring(
                                line.indexOf("Content-Length:") + 16,
                                line.length())).intValue();
            }
        }
        String postData = "";
        // read the post data
        if (postDataI > 0) {
            char[] charArray = new char[postDataI];
            in.read(charArray, 0, postDataI);
            postData = new String(charArray);
        }
        out.println("HTTP/1.0 200 OK");
        out.println("Content-Type: text/html; charset=utf-8");
        out.println("Server: MINISERVER");
        // this blank line signals the end of the headers
        out.println("");
        // Send the HTML page
        out.println("<H1>Welcome to the Mini Server</H1>");
        out.println("<H2>Request Method->" + request_method + "</H2>");
        out.println("<H2>Post->" + postData + "</H2>");
        out.println("<form name=\"input\" action=\"form_submited\" method=\"post\">");
        out.println("Username: <input type=\"text\" name=\"user\"><input type=\"submit\" value=\"Submit\"></form>");
        out.close();
        insocket.close();
    } catch (IOException e) {
        e.printStackTrace();
    }
}

How can it be changed to safe a file (Uploaded through HTTP/1.1 POST REQUEST) form) to disk using this server. Thank you for your time