Class

HTTPSocket

Warning

This item was deprecated in version 2019r1. Please use URLConnection as a replacement.

Description

Used to send and receive data via the HTTP 1.0 protocol.

Methods

Name

Parameters

Returns

Shared

ClearRequestHeaders

Close

Connect

Disconnect

EncodeFormData

Form As Dictionary

String

EndOfFile

Boolean

Flush

Get

URL As String

GetHeaders

URL As String

Listen

Lookahead

[Encoding As TextEncoding]

String

PageHeaders

InternetHeaders

Poll

Post

URL As String

Purge

Read

Count As Integer, [Enc As TextEncoding]

String

ReadAll

[Encoding As TextEncoding]

String

SendRequest

Method As String, URL As String, Timeout As Integer

String

SetFormData

Form As Dictionary

SetPostContent

Content As String, ContentType As String

SetRequestContent

Content As String, ContentType As String

SetRequestHeader

Name As String, Value As String

Write

Data As String

Events

Name

Parameters

Returns

AuthenticationRequired

Realm As String, Headers As InternetHeaders, ByRef Name As String, ByRef Password As String

Boolean

Connected

DownloadComplete

URL As String, HTTPStatus As Integer, Headers As InternetHeaders, File As FolderItem

HeadersReceived

Headers As InternetHeaders, HTTPStatus As Integer

PageReceived

URL As String, HTTPStatus As Integer, Headers As InternetHeaders, Content As String

ProxyAuthenticationRequired

Realm As String, Headers As InternetHeaders, ByRef Name As String, ByRef Password As String

Boolean

ReceiveProgress

BytesReceived As Integer, TotalBytes As Integer, NewData As String

SendProgress

BytesSent As Integer, BytesLeft As Integer

Property descriptions

HTTPSocket.Address

Address As String

The TCP/IP address to try to connect to.

In this example, the address has been entered into a TextField.

TCPSocket1.Address = TextField1.Text

HTTPSocket.BytesAvailable

BytesAvailable As Integer

The number of bytes of data are available in the internal receive buffer.

This property is read-only.

TextField1.Text = Me.BytesAvailable.ToString

HTTPSocket.BytesLeftToSend

BytesLeftToSend As Integer

The number of bytes left in the queue remaining to be sent.

This property is read-only.

This enables you to create a synchronous socket without needing to subclass it.

TextField1.Text = Me.BytesLeftToSend.ToString

HTTPSocket.ErrorCode

ErrorCode As

A special case of LastErrorCode.

Returns the same as LastErrorCode except for these two conditions:

# If Get/Post/GetHeaders/SendRequest times out, then ErrorCode = -1 # When calling Get (the overloaded method that accepts a FolderItem as a parameter), if the file is a directory or could not be created then ErrorCode = 1

HTTPSocket.Handle

Handle As Integer

This is the socket's internal descriptor and it can be used with Declare statements.

This property is read-only.

  • On Windows, Handle is a Socket, suitable for use in Declares on Windows.

  • On macOS and Linux, Handle is a UNIX socket descriptor.

The descriptor is platform-specific. If Handle is less than zero, the descriptor is not available.

HTTPSocket.HTTPProxyAddress

HTTPProxyAddress As String

The proxy address; required only if you are connecting via proxy.

This example specifies the proxy address. The proxy serves as a “middleman" to provide additional security or anonymity.

Me.HTTPProxyAddress = "130.25.0.1"

HTTPSocket.HTTPProxyPort

HTTPProxyPort As Integer

The proxy port; required only if you are connecting via proxy.

This example sets the proxy port.

Me.HTTPProxyPort = 6960

HTTPSocket.HTTPStatusCode

HTTPStatusCode As Integer

Returns the resulting code from the server. This function provides the status code when the socket is used in synchronous mode.

This property is read-only.

This code reads the HTTP status code.

TextField1.Text = Str(Me.HTTPStatusCode)

HTTPSocket.IsConnected

IsConnected As Boolean

Indicates whether the socket is currently connected.

This property is read-only.

For TCPSockets, a connection means you can send and receive data and are connected to a remote machine. For UDPSockets, this means that you are bound to the port and are able to send, receive, join or leave multicast groups, or set socket options.

If EasyUDPSocket1.IsConnected Then
  // proceed using the connection
Else
  MessageBox("Connection failed!")
End If

HTTPSocket.LocalAddress

LocalAddress As String

The local IP address of the computer.

This property is read-only.

Var localIP As String = Socket1.LocalAddress

HTTPSocket.NetworkInterface

NetworkInterface As NetworkInterface

Specifies which network interface the socket should use when binding.

You can get the network interface(s) of the user's computer by calling the GetNetworkInterface method of the System module.

Leaving this property set to Nil will use the currently selected interface. In the case of UDPSockets, if you assign a non-Nil value, the socket may not be able to receive broadcast messages. The behavior is OS-dependent; it appears to work on Windows but not on other supported operating systems. If you wish to send broadcast packets out, then you should not bind to a specific interface because the behavior is undefined.

This example specifies that the TCPSocket will use the first Network Interface on the user's computer.

TCPSocket1.NetworkInterface = System.NetworkInterface(0)

HTTPSocket.Port

Port As Integer

The port to bind on or connect to.

On most operating systems, attempting to bind to a port less than 1024 causes a Error event to fire with an error number 107 unless the application is running with administrative permissions. This is due to security features built into the underlying OS.

You need to set the port property explicitly before any call to Listen or Connect as the Port property will be modified to reflect what the actual bound port is during the various stages of operation.

For instance, if you listen on port 8080 and a connection comes in, you can check the Port property to ensure that you're still listening on port 8080 (that the port hasn't been hijacked). Or, if you connect to a socket on port 8080, once the connection occurs, you can check to see what port the OS has bound you to. This will be a random-seeming port number.

This trick can be very useful when you do things like Listen on port 0. In that case, the OS will pick a port for you and listen on it. Then you can check the Port property to see which port the OS picked. This functionality is used for various protocols, such as FTP.

This example sets the Port to 8080.

TCPSocket1.Port = 8080

HTTPSocket.RemoteAddress

RemoteAddress As String

The address of the remote machine you are connected to.

This property is read-only.

Use this instead of the Address property to determine the address of the machine you are actually connected to.

This example reports the address of the remote machine that the user is connected to. It is in the Connected event.

TextField1.Text = Me.RemoteAddress

HTTPSocket.RequestHeaders

RequestHeaders As InternetHeaders

Request headers are sent to the server along with the action (GET, POST, etc.). They can contain data that the server might use to process your request. Some examples of common request headers are for things such as referring pages, the client name, OS CPU, and so forth.

The default headers are:

Accept:/

Accept-Language:en

Connection:close

HTTPSocket.Yield

Yield As Boolean

When you are using synchronous HTTP, your application may need to wait a noticeable amount of time to get or post a page. Setting Yield to True allows for events and other code to execute while waiting for a page. Yield is relevant when you pass the optional Timeout parameter with Get or GetHeaders. Set Yield to True just prior to a call to any of these methods.

Method descriptions

HTTPSocket.ClearRequestHeaders

ClearRequestHeaders

Clears all of the set request headers. See the description of the SetRequestHeaders method for information on headers.

HTTPSocket.Close

Close

Closes the socket's connection, closes any connections the socket may have, and resets the socket.

The only information that is retained after calling Close is the socket's port, address (in the case of TCPSockets), LastErrorCode properties, and data left in the socket's receive buffer. All other information is discarded.

This example closes the EasyTCPSockets that were open. The sockets were added to the main window.

Connector.Close
Listener.Close

HTTPSocket.Connect

Connect

Attempts to connect.

For TCPSockets, the address and port properties must be set. For UDPSockets, the port property must be set. The Connect method binds a socket to a port. After calling Connect, the Port property will report the actual port you are bound to.

HTTPSocket.Disconnect

Disconnect

Disconnects the socket, resets it, and fires a SocketCore Error event with a 102 error to let you know that the socket has been disconnected.

This example disconnects the EasyTCPSockets that were opened.

Connector.Disconnect
Listener.Disconnect

HTTPSocket.EncodeFormData

EncodeFormData(Form As Dictionary) As String

Takes the key/value pairs from the passed Dictionary and formats them into a URL-encoded String. The result can then be used in the URL to send data to a form with a GET action or as content for a POST.

HTTPSocket.EndOfFile

EndOfFile As Boolean

Returns True when there's no more data left to read.

This code reads the rows and columns of data from a tab-delimited text file into a ListBox:

Var f As FolderItem
Var textInput As TextInputStream
Var rowFromFile, oneCell As String

f = FolderItem.ShowOpenFileDialog("text/plain") // defined as a FileType
If f <> Nil Then
  textInput = TextInputStream.Open(f)
  textInput.Encoding = Encodings.UTF8

  Do
    rowFromFile = textInput.ReadLine
    Var values() As String = rowFromFile.Split(Chr(9))
    ListBox1.ColumnCount = values.Count
    ListBox1.AddRow("")
    Var col As Integer
    For Each value As String In values
      ListBox1.CellTextAt(ListBox1.LastAddedRowIndex, col) = value
      col = col + 1
    End For
  Loop Until textInput.EndOfFile

  textInput.Close
End If

This example reads each pair of bytes from a file and writes them in reverse order to a new file. The user chooses the source file using the Open-file dialog box and saves the new file using the Save as dialog box. The EOF property is used to terminate the Do...Loop.

Var readFile As FolderItem = FolderItem.ShowOpenFileDialog("text")
If readFile <> Nil Then
  Var ReadStream As BinaryStream = BinaryStream.Open(readFile, False)
  ReadStream.LittleEndian = True
  Var writeFile As FolderItem = FolderItem.ShowSaveFileDialog("", "")
  If writeFile <> Nil Then
    Var writeStream As BinaryStream = BinaryStream.Create(writeFile, True)
    writeStream.LittleEndian = True
    Do Until ReadStream.EndOfFile
      writeStream.WriteInt8(ReadStream.ReadInt8)
    Loop
    writeStream = Nil
  End If
  readStream = Nil
End If

HTTPSocket.Flush

Flush

Immediately sends the contents of internal write buffers to disk or to the output stream.

This function can be useful in point-to-point communication over sockets and similar connections: To optimize for transmission performance, some types of output streams try to collect small pieces of written data into one larger piece for sending instead of sending each piece out individually. By calling Flush, the data collection is stopped and the data is sent without further delay, reducing latency.

When using this on a stream that ends up as a file on disk, it is useful, too: Any short parts of previously written data are written to disk right away, ensuring the data is actually on disk if the application terminates abruptly, e.g. due to a crash.

Avoid calling this method too often. For example, do not call it between successive Write calls because you'll slow down performance without getting much benefit.

A typical use case would look like this:

mySocket.Write("you typed: ")
mySocket.Write(key)
mySocket.Write(".")
mySocket.Flush

HTTPSocket.Get

Get(URL As String)

Synchronously downloads the content from the URL directly to the FolderItem. When the download has finished, True is returned if successful, False if there was an error. Timeout is the number of seconds to wait for the result. ErrorCode is -1 if the Timeout value is reached.

For the synchronous version of these methods, set the Yield property to True to allow for background activities while waiting.

HTTPSocket.GetHeaders

GetHeaders(URL As String)

Synchronously Requests only the page headers from the specified URL. The headers are return as an InternetHeaders.

When running synchronously, set the Yield property to True to allow for background activities while waiting.

HTTPSocket.Listen

Listen

Attempts to listen for incoming connections on the currently specified port.

After calling Listen, the Port property will report the actual port you are bound to.

HTTPSocket.Lookahead

Lookahead([Encoding As TextEncoding]) As String

Returns a String, containing the data that is available in the internal queue without removing it.

The optional Encoding parameter enables you to specify the text encoding of the data to be returned. The default is Nil. Use the Encodings module to specify an encoding.

This example adds the contents of the internal queue to a TextArea. The Listener EasyTCPSocket has been added to the window.

TextArea1.AddText(listener.Lookahead)

HTTPSocket.PageHeaders

PageHeaders As InternetHeaders

Provides access to the headers received from the server. This can be used to access the headers in synchronous mode.

HTTPSocket.Poll

Poll

Polls the socket manually, which allows a socket to be used synchronously.

The EasyTCPSocket "Listener" has been added to the window.

Listener.Poll

HTTPSocket.Post

Post(URL As String)

Synchronously issues a POST command to the URL and downloads the response directly to the FolderItem. When the download has finished, True is returned if successful, False if there was an error. TimeOut is the number of seconds to wait for the result.

For the synchronous versions of this method, set the Yield property to True to allow for background activities while waiting.

This example does a synchronous POST to a service that returns what you POSTed to it as JSON:

Var d As New Dictionary

d.Value("Test") = "TestValue"
d.Value("Value2") = "Testing"

Socket.SetFormData(d)

// This service returns the post data as the result
Var result As String
result = Socket.Post("http://httpbin.org/post", 30) // Synchronous

result = DefineEncoding(result, Encodings.UTF8)

MessageBox(result)

To do this asynchronous, call Post without a timeout:

Var d As New Dictionary

d.Value("Test") = "TestValue"
d.Value("Value2") = "Testing"

Socket.SetFormData(d)

// This service returns the post data as the result
Socket.Post("http://httpbin.org/post")

The results will be available in the PageReceived event handler in the content parameter.

Sub PageReceived(url As String, httpStatus As Integer, headers As InternetHeaders, content As String)
  Var data As String
  data = DefineEncoding(content, Encodings.UTF8)

  ResultArea.Value = data
End Sub

HTTPSocket.Purge

Purge

Removes all data from the socket's internal receive buffer. It does not affect the socket's internal send buffer.

Listener.Purge

HTTPSocket.Read

Read(Count As Integer, [Enc As TextEncoding]) As String

Reads Count bytes from the input stream and returns a String.

If provided, the optional parameter Enc specifies the text encoding to be defined for the String to be read.

If Count is higher than the amount of bytes currently available in the stream, all available bytes will be returned. Therefore, make sure to always consider the case that you get less than you requested. To see if you received all requested bytes, check the returned string's String.Bytes property (avoid using Length as it may give a different number if the encoding is not nil).

If not enough memory is available, you get back an empty string.

This example reads the first 1000 bytes from a BinaryStream.

Var readFile As FolderItem = FolderItem.ShowOpenFileDialog("text/plain")
If readFile <> Nil Then
  Var ReadStream As BinaryStream = BinaryStream.Open(readFile, False)
  ReadStream.LittleEndian = True
  TextArea1.Text = ReadStream.Read(1000, Encodings.UTF8)
End If

HTTPSocket.ReadAll

ReadAll([Encoding As TextEncoding]) As String

Reads all the data from the internal buffer.

This example reads all the data in the buffer into a TextArea.

TextField1.AddText(listener.ReadAll)

HTTPSocket.SendRequest

SendRequest(Method As String, URL As String, Timeout As Integer) As String

Allows the user to synchronously send a request using an HTTP method other than GET or POST. Supply the method as a String, URL as a String and a FolderItem. Return a Boolean to indicate if it was successful. Data is saved to the FolderItem.

Common others methods are OPTIONS, HEAD, PUT, DELETE, TRACE and CONNECT as per RFC 2616 describing the HTTP 1.1 protocol.

HTTPSocket.SetFormData

SetFormData(Form As Dictionary)

Takes the key/value pairs from the passed Dictionary and converts it to a URL-encoded String.

HTTPSocket.SetPostContent

SetPostContent(Content As String, ContentType As String)

Sets the content data and content type to be sent to the server for a POST command.

HTTPSocket.SetRequestContent

SetRequestContent(Content As String, ContentType As String)

Sets the content data and content type to be sent to the server for any command except HEAD.

If you will be reusing a socket without using the New operator, you must clear this value for requests that do not have content associated with them. For instance, If you do a POST with content followed by a GET that should not have content, you should set the content to an empty string.

Set request content:

Dim data As String = "ID=1234"
MySocket.SetRequestContent(data, "application/x-www-form-urlencoded")

HTTPSocket.SetRequestHeader

SetRequestHeader(Name As String, Value As String)

Sets the value of a request header.

Request headers are sent to the server along with the action (GET, POST, etc.). They can contain data that the server might use to process your request. Some examples of common request headers are for things such as referring pages, the client name, OS CPU, and so forth.

This example changes the user agent:

HTTPSocket1.SetRequestHeader("User-Agent:", "CustomUserAgentString")

HTTPSocket.Write

Write(Data As String)

Writes the passed data to the output stream.

Note that in order to make sure that the data actually ends up on disk or gets sent to the socket it is connected to, the stream must either get closed or the Flush method be called. Otherwise, the data, if small, may end up temporarily in a write buffer before either a certain time has passed or more data is written. This buffering increases performance when writing lots of small pieces of data, but may be causing unwanted delays when another process, e.g. the other end of a socket connection, is waiting for the data. Consider calling the Flush method to reduce latencies that this buffering may cause in such cases.

If Write fails, an IOException will be raised.

This example displays the Save As dialog box and writes the contents of the TextArea1 to a text file.

Var f As FolderItem
Var stream As BinaryStream
f = FolderItem.ShowSaveFileDialog(FileTypes1.Text, "Untitled.txt")
If f<> Nil Then
  stream = BinaryStream.Create(f, True)
  stream.Write(TextArea1.Text)
  stream.Close
End If

Event descriptions

HTTPSocket.AuthenticationRequired

AuthenticationRequired(Realm As String, Headers As InternetHeaders, ByRef Name As String, ByRef Password As String) As Boolean

Executes when a site that requires authentication connects. AuthenticationRequired also supports Digest authentication.

HTTPSocket.Connected

Connected

Executes when the connection is established with the server.

HTTPSocket.DownloadComplete

DownloadComplete(URL As String, HTTPStatus As Integer, Headers As InternetHeaders, File As FolderItem)

Executes when a download is complete after using the Get or Post methods and passing the optional parameter. URL contains the URL that was downloaded. File is the FolderItem the data was downloaded to, and Headers is a dictionary of the HTTP headers that were returned by the server. The HTTPStatus code is also passed to this event. These codes are used for messages such as "Page not found" (error 404), and so forth.

HTTPSocket.HeadersReceived

HeadersReceived(Headers As InternetHeaders, HTTPStatus As Integer)

Executes when the headers have been retrieved from the server.

HTTPSocket.PageReceived

PageReceived(URL As String, HTTPStatus As Integer, Headers As InternetHeaders, Content As String)

Executes when a new page has been retrieved from the server. It provides the URL that was requested and the HTTP headers from the web server. The HTTPStatus code is also passed to this event. These codes are used for messages such as "Page not found" (error 404), and so forth.

HTTPSocket.ProxyAuthenticationRequired

ProxyAuthenticationRequired(Realm As String, Headers As InternetHeaders, ByRef Name As String, ByRef Password As String) As Boolean

Executes when a site that requires via proxy authentication connects. ProxyAuthenticationRequired also supports Digest authentication.

HTTPSocket.ReceiveProgress

ReceiveProgress(BytesReceived As Integer, TotalBytes As Integer, NewData As String)

Provides the current number of bytes received and the total number of bytes (if available). It executes periodically during the download process.

HTTPSocket.SendProgress

SendProgress(BytesSent As Integer, BytesLeft As Integer)

Occurs when your network provider queues your data in chunks and is about to send the next chunk.

The parameters indicate the amount of progress that has been made during the send. Returns a Boolean.

Returning True from this event causes the send to be cancelled. This does not close the socket's connection; it only clears the buffer. After all of the data has been transferred you will get a final SendProgress event followed by a SendComplete event.

bytesSent is the number of bytes that were sent in the chunk, not the total number of bytes sent.

Notes

Note

If you need HTTP 1.1 support, use URLConnection instead.

Use the HTTPSocket class to send and receive data via the HTTP protocol. Since this is a subclass of the TCPSocket class, all the standard socket APIs are also available. To perform secure communications (via HTTPS), use the URLConnection class instead. It is otherwise identical, except that it is subclassed from SSLSocket instead of TCPSocket. This makes all the options for encrypted communications available to URLConnection objects.

If you use a constructor in a subclass of HTTPSocket, you must call the super class's constructor in your subclass's constructor. The subclass fail when you try to download.

When using the optional Timeout parameter of the Get or GetHeaders methods the page will be received or posted in a synchronous manner. That is, your app will wait until the page has been received or posted before it proceeds. If Timeout is set to zero, the socket will wait indefinitely or until it receives an error.

To use synchronous mode, pass the optional parameter. For example,

Dim http As New HTTPSocket
MsgBox(http.Get("http://www.example.com", 30))

When using synchronous mode, you can set the Yield property to True to tell the socket to yield time to other events and code to execute while waiting. Insert a statement such as:

http.Yield = True

to allow background processes to execute while waiting.

App transport security

Starting with OS X 10.11 and 2018r4, your apps have to use secure "https" connections or you will get this error: "The resource could not be loaded because the App Transport Security policy requires the use of a secure connection". You can work around this by providing a plist with your app to indicate what non-secure URLs you are using. For more information:

Xojo cloud

Web apps running on Xojo Cloud first have to use the FirewallPort class to open the port used to connect to an outside web server.

Sample code

The following example retrieves the specified URL synchronously:

Dim socket1 As New HTTPSocket
Dim data As String = socket1.Get("http://www.example.com/", 30)

For asynchronously transfers you need to subclass HTTPSocket, call get without timeout parameter and get result in PageReceived event.

The following example posts a simple form:

Dim form As Dictionary
Dim socket1 As New HTTPSocket

// create and populate the form object
form = New Dictionary
form.Value("firstname") = "Bob"
form.Value("lastname") = "Brown"

// setup the socket to POST the form
socket1.SetFormData(form)
socket1.Post("http://www.myformlocation.com/form.php")

To send one or more cookies with an HTTP request:

socket.SetRequestHeader("Cookie", Join(Array(cookie1, cookie2), "; "))

Compatibility

All project types on all supported operating systems.