|
|
(VB.NET) Receiving a String
Demonstrates how to receive character data on a socket connection. The code for this example immediately follows the session logs (below). You should first read throught the code w/ comments and then refer back to these session logs...
SessionLog for 1st ReceiveString method call
SPACE chars are shown as \x20. It is easy to see that
the accented characters (á, é, í, ó, ú, ý) are each represented
by a single byte in the received data: \xE1, \xE9, 0xED, \xF3, \xFA, and \xFD.
ReceiveString1: HTTP/1.1\x20200\x20OK\r\n
Content-Length:\x20140\r\n
Content-Type:\x20text/html\r\n
Last-Modified:\x20Thu,\x2001\x20Oct\x202009\x2012:29:48\x20GMT\r\n
Accept-Ranges:\x20bytes\r\n
ETag:\x20\"2e66a6dd9242ca1:28b\"\r\n
Server:\x20Microsoft-IIS/6.0\r\n
X-Powered-By:\x20ASP.NET\r\n
Date:\x20Thu,\x2001\x20Oct\x202009\x2013:56:53\x20GMT\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\xE1,\x20\xE9,\x20\xED,\x20\xF3,\x20\xFA,\x20\xFD\r\n
\r\n
SessionLog for 2nd ReceiveString method call
It is easy to see that
the accented characters (á, é, í, ó, ú, ý) are each represented
by two bytes in the received data: \xC3\xA1, \xC3\xA9, etc.
ReceiveString1: HTTP/1.1\x20200\x20OK\r\n
Content-Length:\x20141\r\n
Content-Type:\x20text/html\r\n
Last-Modified:\x20Thu,\x2001\x20Oct\x202009\x2012:29:48\x20GMT\r\n
Accept-Ranges:\x20bytes\r\n
ETag:\x20\"a6968dd9242ca1:28b\"\r\n
Server:\x20Microsoft-IIS/6.0\r\n
X-Powered-By:\x20ASP.NET\r\n
Date:\x20Thu,\x2001\x20Oct\x202009\x2013:56:53\x20GMT\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\r\n
\xC3\xA1,\x20\xC3\xA9,\x20\xC3\xAD,\x20\xC3\xB3,\x20\xC3\xBA,\x20\xC3\xBD\r\n
\r\n
' This example requires the Chilkat API to have been previously unlocked.
' See Global Unlock Sample for sample code.
Dim socket As New Chilkat.Socket
' To demonstrate receiving character (i.e. not binary) data,
' this example will connect to the chilkatsoft.com web server
' and download a very short and simple HTML page.
' (Note: You would typically use the Chilkat HTTP component
' to communicate with a web server. We only do it here to
' provide an example that is runnable such that socket peer
' (i.e. the other end of the socket connection) is already
' available.
' So.. let's first connect the socket to the remote peer.
Dim ssl As Boolean = False
Dim maxWaitMillisec As Integer = 20000
Dim port As Integer = 80
Dim success As Boolean = socket.Connect("www.chilkatsoft.com",port,ssl,maxWaitMillisec)
If (success <> True) Then
Debug.WriteLine(socket.LastErrorText)
Exit Sub
End If
' Set maximum timeouts for reading an writing (in millisec)
socket.MaxReadIdleMs = 10000
socket.MaxSendIdleMs = 10000
' Send a simple HTTP GET request to download
' an HTML file on the server named "iso_chars.html"
' This web page contains the following characters
' using the iso-8859-1 encoding:
' á, é, í, ó, ú, ý
' The Chilkat Socket API has a convenience method named
' BuildHttpGetRequest to make it easy to send an HTTP GET
' for a URL:
Dim getRequest As String
getRequest = socket.BuildHttpGetRequest("http://www.chilkatsoft.com/iso_chars.html")
' Send the GET request to the HTTP server:
success = socket.SendString(getRequest)
If (success <> True) Then
Debug.WriteLine(socket.LastErrorText)
Exit Sub
End If
' Before calling ReceiveString to get the HTTP response,
' let's turn on session logging so we can examine the
' actual bytes received:
socket.KeepSessionLog = True
' IMPORTANT:
' Tell the component the character encoding of the string
' data to be received by setting the StringCharset property.
' This is extremely important. The socket component/library must know how
' to interpret the received bytes. For example,
' the character "á" will be represented as a single byte
' having the hex value 0xE1 when encoded using iso-8859-1,
' but will arrive as a sequence of 2 bytes having the values
' 0xC3 0xA1 when encoded using utf-8.
' Given that strings are returned as Unicode or utf-8 in most
' programming languages, the socket component must know how
' to interpret the received bytes to properly construct the
' string to be returned to the caller.
socket.StringCharset = "iso-8859-1"
' OK, get the response:
Dim resp As String = socket.ReceiveString()
If (socket.LastMethodSuccess <> True) Then
Debug.WriteLine(socket.LastErrorText)
Exit Sub
End If
' Examine the received string:
Debug.WriteLine(resp)
Debug.WriteLine("---------------------------")
' Important: ReceiveString may not receive the entire response.
' It simply receives whatever data is already available from
' the connected peer. To simplify the example, we're assuming
' the complete response is received -- and it is likely
' because the response is short.
' OK, let's examine the session log to see the actual bytes
' received. (The session logging was turned on just
' before the call to ReceiveBytes, so we won't see the activity
' prior to it.)
' The SessionLogEncoding property controls the output format
' of the session log. It defaults to "esc" for escaped ASCII, which
' is a good way of viewing mostly US-ASCII character data.
' We'll be able to see the binary bytes in between the printable
' ASCII characters as hex values escaped with "\x".
Debug.WriteLine(socket.SessionLog)
' (Refer to the SessionLog for the 1st ReceiveString above for the expected results.)
' Close the connection with the server
' Wait a max of 20 seconds (20000 millsec)
success = socket.Close(20000)
' -----------------------------------------------------------------
' Now we'll download a utf-8 encoded HTML page
' to see how the bytes received for the same characters
' are different. The Socket component must know how
' to interpret these bytes as characters, and (as discussed
' before) this is the purpose of the StringCharset property.
' Connect to the chilkatsoft.com HTTP server again.
success = socket.Connect("www.chilkatsoft.com",port,ssl,maxWaitMillisec)
If (success <> True) Then
Debug.WriteLine(socket.LastErrorText)
Exit Sub
End If
' This time, get an HTML page where the characters
' are encoded using utf-8.
getRequest = socket.BuildHttpGetRequest("http://www.chilkatsoft.com/utf8_chars.html")
' Send the GET request to the HTTP server:
success = socket.SendString(getRequest)
If (success <> True) Then
Debug.WriteLine(socket.LastErrorText)
Exit Sub
End If
' Tell the component to interpret the received bytes as
' utf-8. (This only applies to methods that receive strings,
' such as ReceiveString, ReceiveUntilMatch, etc.
' Methods that receive bytes, such as ReceiveBytes, do
' not try to interpret the bytes received from the connected
' peer -- they simply return the bytes received.)
socket.StringCharset = "utf-8"
' Clear the session log so we can examine it again for the next
' call to ReceiveString:
socket.ClearSessionLog()
resp = socket.ReceiveString()
If (socket.LastMethodSuccess <> True) Then
Debug.WriteLine(socket.LastErrorText)
Exit Sub
End If
' The characters should display correctly:
Debug.WriteLine("---------------------------")
Debug.WriteLine(resp)
Debug.WriteLine("---------------------------")
' Examine the session log. You'll see that the actual bytes
' received for the characters were 2-bytes/char. Because
' the StringCharset was correctly set, the socket component
' knew how to interpret the bytes to arrive at the appropriate
' characters.
Debug.WriteLine(socket.SessionLog)
' (Refer to the SessionLog for the 2nd ReceiveString above for the expected results.)
success = socket.Close(20000)
|
