SocketRead (Function)

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Number of transmitted bytes
Communication with robots or with non-WINDEV applications
Transmission between two computers that use character strings in different formats (UNICODE and ANSI)
Required permissions

WINDEV

WEBDEV

WINDEV Mobile

Others

See also

SocketRead (Function)

In french: SocketLit

Retrieves a message sent by another socket. This function can be used on a client computer or on a server.

Remarks:

UDP socket: The UDP protocol being a "connectionless protocol", when retrieving the message, WINDEV saves the IP address and port of the computer that sent the message. This information is returned by SocketClientInfo.
SSL socket: SocketRead can be used with the SSL sockets.

Reminder: A socket is a communication resource used by the applications to communicate between computers regardless of the network type.

Versions 15 and later

This function is now available for Android applications.

New in version 15

This function is now available for Android applications.

Versions 17 and later

This function is now available for iPhone/iPad applications.

This function is now available for Windows Phone applications.

New in version 17

This function is now available for iPhone/iPad applications.

This function is now available for Windows Phone applications.

This function is now available for iPhone/iPad applications.

This function is now available for Windows Phone applications.

Versions 18 and later

This function is now available in Android Widget mode.

New in version 18

This function is now available in Android Widget mode.

Versions 23 and later

This function is now available in Universal Windows 10 App mode.

New in version 23

This function is now available in Universal Windows 10 App mode.

Example

See additional examples

// Display the incoming message
Info(SocketRead("Server", False))

Syntax

<Result> = SocketRead(<Socket name> [, <Undefined Wait> [, <Maximum timeout> [, <Maximum Number of Bytes>]]])

<Result>: Buffer or character string

Message read.
Empty buffer or empty string ("") if no message was received.

<Socket name>: Character string (with quotes)

Name of socket that received the message.
In the WINDEV applications:
this name was defined on the server:
by SocketCreate or SocketCreateInfrared (for a simplified server).
by SocketAccept (for a standard server).
this name was defined on the client by SocketConnect or SocketConnectInfrared.

<Undefined Wait>: Optional boolean

True (default value): undefined wait for a client message.
False: wait until the <Maximum time-out>.

<Maximum timeout>: Optional integer or optional Duration

Maximum time-out (in milliseconds) of a client message if the undefined wait is set to False. This parameter can correspond to:
an integer corresponding to the number of milliseconds,
a Duration variable,
Versions 23 and later
the direct indication of duration (1 s or 10 ms for example).
New in version 23
the direct indication of duration (1 s or 10 ms for example).
the direct indication of duration (1 s or 10 ms for example).
This time-out is set to 1000 milliseconds by default (1 second).

<Maximum Number of Bytes>: Optional integer

Maximum number of characters that can be transmitted. The number of characters received is not guaranteed.
This parameter is taken into account only if the SocketNoEndTag constant is specified in SocketChangeTransmissionMode. Otherwise, this parameter is ignored.
This parameter is set to 4096 bytes by default.

Remarks

Number of transmitted bytes

<Maximum number of bytes> corresponds to the maximum number of characters that can be transmitted. The number of characters received is not guaranteed.

SocketRead reads a network frame and returns it immediately, without transformation. However, the size of a network frame depends on several factors (network setting, speed and traffic on the network, ...).

SocketWrite sends (if possible) the buffer passed in parameter in a single frame. If this frame is not accepted by the network, the buffer can be divided into several frames (or the other way round, the network can merge the messages into a single frame to optimize the bandwidth).

To respect the integrity of the transmitted messages, you must use a native WINDEV and WEBDEV protocol (with the SocketSizeAtBeginning or SocketEndTag constants of SocketChangeTransmissionMode) or you must implement a specific protocol.

Communication with robots or with non-WINDEV applications

To simplify the exchanges of data by socket, a transmission mode is initialized by default.

For a communication with an external module (non-WINDEV application, robot, ...), this transmission mode can prevent the communications from operating properly.

SocketChangeTransmissionMode is used to change this transmission mode: the SocketNoEndTag constant allows you not to modify the frames read and written.

Transmission between two computers that use character strings in different formats (UNICODE and ANSI)

Some conversions may be required when messages are transmitted between two computers that use character strings in different formats (Windows (ANSI) and Windows Mobile (UNICODE) for example). These conversions can be performed by AnsiToUnicode and UnicodeToAnsi.

Required permissions

The call to this function modifies the permissions required by the application.
Required permission : INTERNET
This permission allows the applications to open the network sockets.

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