base.Channel.openServerSocket
Open a TCP server socket channel.
Syntax
openServerSocket(
interface STRING,
port INTEGER,
mode STRING )
- interface is the name of the network interface to be used.
- port is the port number of the service.
- mode is the open mode. Only
"u"
is allowed (combined with"b"
if needed).
Usage
The openServerSocket()
method initializes the channel object to
listen to a given TCP interface and port.
The server socket accepts multiple client connections. After calling the
openServerSocket()
method, a call to readLine()
waits until the
first client connects and returns after reading a complete line. Only one client connection can be
serviced at time: it's not possible to select a specific client connection. A client connection must
be closed by writing the EOF character to the channel. The EOF character is ASCII 26. Do not call
base.Channel.close()
to close a client/server connection; this would close the
server socket and reject any pending client connection. The next call to readLine()
after writing EOF will wait until the next client connects or select the next pending client.
Pay attention to the character set used by the network protocol you want to use by opening a channel with this method. The protocol must be based on ASCII, or must use the same character set as the application.
The interface parameter defines the network interface to be used,
in case the server uses different network adapters. Use NULL
to listen to all
network interfaces, or when the server has only one network interface.
The port parameter defines the TCP port to listen to.
The opening mode must be "u"
, to read and write
from/to the socket. The method will raise error -8085 if the mode is different from
"u"
.
The "u"
mode can be combined with the "b"
binary mode, to avoid
CR/LF translation on Windows®
platforms.
The method raises error -8084 if the socket cannot be opened.
Example
MAIN
DEFINE io base.Channel
DEFINE s STRING
LET io = base.Channel.create()
CALL io.openServerSocket("127.0.0.1", 4711, "u")
WHILE TRUE
LET s = io.readLine()
CALL io.writeLine(s)
-- next line closes the current connection
CALL io.writeLine(ASCII 26) -- EOF
END WHILE
END MAIN