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 applications to communicate from one computer to another regardless of the type of network.

Example

See additional examples

// Add received messages in a Table control
TableAdd(TABLE_Table1, "1" + TAB + SocketRead("Server", False) + ...
TAB + SocketClientInfo("server", SocketAddress) + ...
TAB + SocketClientInfo("server", SocketPort))

WHILE SocketExist("MySocket") = True
sMsg is string = SocketRead("MySocket", True)
IF sMsg <> "" THEN
ListAdd(LIST_Messages, Now() + " " + sMsg)
END
END

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

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

<Undefined wait>: Optional boolean

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

<Maximum timeout>: Optional integer or optional Duration

Maximum timeout (in milliseconds) of a client message if the undefined wait is set to False. This parameter can be:
an integer corresponding to the number of milliseconds,
a Duration variable,
the duration in a readable format (e.g., 1 s or 10 ms).
By default, this timeout is set to 1000 milliseconds (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 transforming it. 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 as 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)

It may be necessary to convert strings in order to send messages between two computers that uses different encodings (e.g., ANSI and UNICODE). These conversions can be made 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.

Business / UI classification: Business Logic

Component: wd300com.dll