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Sockets and Internet Protocols

How to get the file length before download

Greenhorn

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posted 18 years ago

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Dear All
I am trying to get the size of a file before downloading it. I cannot use the URL method GetContentLength because I'm using Sockets not URLs so is there any other way to do this?
Thanks

Dirk Schreckmann

Sheriff

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posted 18 years ago

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Welcome to JavaRanch!
Moving this to the Sockets forum...

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Ernest Friedman-Hill

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posted 18 years ago

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When you say you're using sockets, do you mean a custom client and server, or do you mean you're using raw sockets to talk to an HTTP or FTP (or other) server?

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Zac Nahas

Greenhorn

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posted 18 years ago

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I am using the object Socket to do basic connection to download a file but I need to know the size of the file ahead of time. So is there any socket function of HTTP function that can find the file size?

Zac Nahas

Greenhorn

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posted 18 years ago

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I am using the object Socket to do basic connection to download a file but I need to know the size of the file ahead of time. So is there any socket function OR HTTP function that can find the file size?
PS: I posted again to correct the or. Sorry for the typo.

Ernest Friedman-Hill

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posted 18 years ago

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Well, you didn't quite answer my question, but I'll assume that you're using plain Sockets to connect to a Web server to download the file.
If you use HTTP 1.0 commands to fetch the file, you'll get a "Content-Length:" header which you can parse to get the length of the file -- i.e., like the below. The line "GET / HTTP/1.0" is the key thing you have to send; the Content-Length header will come back and you can parse it.
It's a lot easier to use URLConnection, though!
$ telnet localhost 80
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
GET / HTTP/1.0
HTTP/1.1 200 OK
Date: Wed, 25 Feb 2004 22:13:40 GMT
Server: Apache/2.0.48 (Unix) DAV/2 SVN/1.0.0
Last-Modified: Mon, 23 Feb 2004 21:22:09 GMT
ETag: "50421c-ae5-a0490240"
Accept-Ranges: bytes
Content-Length: 2789
Connection: close
Content-Type: text/html; charset=ISO-8859-1
<!doctype html public "-//w3c//dtd html 4.0 transitional//en">
<html>
<head>

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Zac Nahas

Greenhorn

Posts: 6

posted 18 years ago

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Thank you for your respone.Your assumption is correct. However, the solution you suggested didn't work well
I used:
telnet yahoo.com 80
The response was:
Trying 66.218.71.198...
Connected to yahoo.com.
Escape character is '^]'.
I then typed:
GET / HTTP/1.0
No response:
If I used instead
GET /HTTP/1.0
I get the index.html file by the GET command. So what is the problem?

Ernest Friedman-Hill

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posted 18 years ago

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Look back carefull at the transcript I showed you. When you use the HTTP/1.0 form, you have to enter a blank line before you'll get a response. That's because HTTP/1.0 requests can themselves include headers; the extra blank line indicates the end of the request.
I'm guessing that asking Yahoo for a non-existent page just returns their index page; smooshing the "/" and "HTTP/1.0" together makes it look like an HTTP 0.9 reqeust for a non-existent page.

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