|
dev
newsgroups
|
|||||||||||||||||||||||
|
|||||||||||||||||||||||
Re: HowTo, Download first 1024 bytes of file ONLY?> Basically, the title explains it. Well, I'm no specialist (I started programming C# err... yesterday.> > I want to be able to read the first n bytes (say, 1024 bytes) of any > file (text or binary) off the internet in my vb.net application. I > specifically do not want to download the whole file (which in most > cases will be significantly large compared to the portion i do want). But, how about something like this horrible non-compilable code snippet (most of which was stolen from a Microsoft C# socket example) : int port = PORT_NUMBER; string server = SERVER_NAME; Socket s = null; IPHostEntry hostEntry = null; hostEntry = Dns.GetHostEntry(server); foreach (IPAddress address in hostEntry.AddressList) { IPEndPoint ipe = new IPEndPoint(address, port); Socket tempSocket = new Socket(ipe.AddressFamily, SocketType.Stream, ProtocolType.Tcp); try { tempSocket.Connect(ipe); } catch { } finally { } if (tempSocket.Connected) { s = tempSocket; break; } else { // explain to the user why we can't service the request, // and either try again or abend. DialogResult dr = MessageBox.Show( "We don't appear to be able to connect to the server. Is it running ?", "Socket Error", MessageBoxButtons.RetryCancel, MessageBoxIcon.Exclamation, MessageBoxDefaultButton.Button1); continue; } } // Send request to the server. s.Send(Request, Request.Length, 0); int bytes = 0; i = 0; // The following will block until the data is transmitted. for (; ; ) { // This returns a stream of bytes NumberOfBytes = s.Receive(buffer, buffer.Length, 0); string blah = Encoding.ASCII.GetString(buffer, 0, NumberOfBytes); // Add logic so you know when to stop // } s.Close(); > Ok, I've had my moment of publicly whining (this is what happens IFYP. I've got this spiffy MSDN Universal thing, and I'd be dead in the> after 3-full days of performing errant google searches). water without Google. jd John,
This shouldn't be to hard, the webrequest/webresponse objects (or derivitives) that allow downloading a file from the internet can do so in chunks (such as 1024). I am doing that for downloading updates for my app. Show quote "John Daragon" <j***@argv.co.uk> wrote in message news:4429ac6b$0$23297$db0fefd9@news.zen.co.uk... > NutsAboutVB wrote: >> Basically, the title explains it. >> >> I want to be able to read the first n bytes (say, 1024 bytes) of any >> file (text or binary) off the internet in my vb.net application. I >> specifically do not want to download the whole file (which in most >> cases will be significantly large compared to the portion i do want). > > Well, I'm no specialist (I started programming C# err... yesterday. > > But, how about something like this horrible non-compilable code snippet > (most of which was stolen from a Microsoft C# socket example) : > > int port = PORT_NUMBER; > string server = SERVER_NAME; > > Socket s = null; > IPHostEntry hostEntry = null; > hostEntry = Dns.GetHostEntry(server); > > foreach (IPAddress address in hostEntry.AddressList) > { > IPEndPoint ipe = new IPEndPoint(address, port); > Socket tempSocket = new Socket(ipe.AddressFamily, > SocketType.Stream, ProtocolType.Tcp); > > try > { > > tempSocket.Connect(ipe); > > } > catch { } > finally > { > } > > if (tempSocket.Connected) > { > s = tempSocket; > break; > } > else > { > // explain to the user why we can't service the > request, > // and either try again or abend. > > DialogResult dr = MessageBox.Show( > > "We don't appear to be able to connect > to the server. Is it running ?", "Socket Error", > MessageBoxButtons.RetryCancel, > MessageBoxIcon.Exclamation, > MessageBoxDefaultButton.Button1); > > > continue; > } > > } > > // Send request to the server. > > s.Send(Request, Request.Length, 0); > > int bytes = 0; > i = 0; > // The following will block until the data is transmitted. > for (; ; ) > { > > // This returns a stream of bytes > NumberOfBytes = s.Receive(buffer, buffer.Length, 0); > string blah = Encoding.ASCII.GetString(buffer, 0, > > NumberOfBytes); > > // Add logic so you know when to stop > // > } > > s.Close(); > >> Ok, I've had my moment of publicly whining (this is what happens >> after 3-full days of performing errant google searches). > > IFYP. I've got this spiffy MSDN Universal thing, and I'd be dead in the > water without Google. > > jd Hello,
I was hoping to not hear the words 'socket programming', since it does remind me of the tedious hit and miss days of socket hackery back in VB6 times - wasn't my fav. thing to work with, but I am sure sockets in ..net 2.0 is much more user friendly. Thank you for the code. Regarding webrequest/webresponse, are you sure about this? Since when i did look into the documentation i didn't read anything about this. Excuse the delay in my response (it was Formula 1 weekend in melbourne australia, and as you probably know, getting back into 'programmer mode' does take some time). Show quote :) I don't have the code with me at this location, but yes I am sure that I am
getting it in 1024 chunks and then doing as I wish with it. webrequest/response I think are abstract classes--could be wrong....seems there was an httpwebresponse object or request object that I was actually using. A quick search produced this: http://www.codeguru.com/Csharp/Csharp/cs_network/internetweb/article.php/c7005/ Maybe it will help you. I am not certain but I think you get the stream and read it little by little and just by having that stream, doesn't mean it has all been downloaded, so I assume you could get 1024 bytes from it and then abort some how. HTH, Shane Show quote "SStory" <nospam@nospam.com> wrote in message news:uHqKQKrUGHA.4740@TK2MSFTNGP14.phx.gbl... > John, > > This shouldn't be to hard, the webrequest/webresponse objects (or > derivitives) that allow downloading a file from the internet can do so in > chunks (such as 1024). > > I am doing that for downloading updates for my app. > > "John Daragon" <j***@argv.co.uk> wrote in message > news:4429ac6b$0$23297$db0fefd9@news.zen.co.uk... >> NutsAboutVB wrote: >>> Basically, the title explains it. >>> >>> I want to be able to read the first n bytes (say, 1024 bytes) of any >>> file (text or binary) off the internet in my vb.net application. I >>> specifically do not want to download the whole file (which in most >>> cases will be significantly large compared to the portion i do want). >> >> Well, I'm no specialist (I started programming C# err... yesterday. >> >> But, how about something like this horrible non-compilable code snippet >> (most of which was stolen from a Microsoft C# socket example) : >> >> int port = PORT_NUMBER; >> string server = SERVER_NAME; >> >> Socket s = null; >> IPHostEntry hostEntry = null; >> hostEntry = Dns.GetHostEntry(server); >> >> foreach (IPAddress address in hostEntry.AddressList) >> { >> IPEndPoint ipe = new IPEndPoint(address, port); >> Socket tempSocket = new Socket(ipe.AddressFamily, >> SocketType.Stream, ProtocolType.Tcp); >> >> try >> { >> >> tempSocket.Connect(ipe); >> >> } >> catch { } >> finally >> { >> } >> >> if (tempSocket.Connected) >> { >> s = tempSocket; >> break; >> } >> else >> { >> // explain to the user why we can't service the >> request, >> // and either try again or abend. >> >> DialogResult dr = MessageBox.Show( >> >> "We don't appear to be able to connect >> to the server. Is it running ?", "Socket Error", >> MessageBoxButtons.RetryCancel, >> MessageBoxIcon.Exclamation, >> MessageBoxDefaultButton.Button1); >> >> >> continue; >> } >> >> } >> >> // Send request to the server. >> >> s.Send(Request, Request.Length, 0); >> >> int bytes = 0; >> i = 0; >> // The following will block until the data is transmitted. >> for (; ; ) >> { >> >> // This returns a stream of bytes >> NumberOfBytes = s.Receive(buffer, buffer.Length, 0); >> string blah = Encoding.ASCII.GetString(buffer, 0, >> >> NumberOfBytes); >> >> // Add logic so you know when to stop >> // >> } >> >> s.Close(); >> >>> Ok, I've had my moment of publicly whining (this is what happens >>> after 3-full days of performing errant google searches). >> >> IFYP. I've got this spiffy MSDN Universal thing, and I'd be dead in the >> water without Google. >> >> jd > >  |
|||||||||||||||||||||||
Other interesting topics