Open a TCP client socket channel.


   host STRING,
   port INTEGER,
   mode STRING,
   timeout INTEGER )
  1. host is the name of the host machine you want to connect to.
  2. port is the port number of the service.
  3. mode is the open mode. Can be "r", "w" or "u" (combined with "b" if needed).
  4. timeout is the timeout in seconds. -1 indicates no timeout (wait forever).


Use the openClientSocket() method to establish a TCP connection to a server.

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 host parameter defines the host name of the server.

The port parameter defines the TCP port to connect to.

The opening mode can be one of the following:
  • r: For read mode: only to read from the socket
  • w: For write mode: only to write to the socket
  • u: For read and write mode: To read and write from/to the socket
Any of these modes can be followed by b, to use binary mode and avoid CR/LF translation on Windows® platforms.
Note: The binary mode is only required in specific cases, and will only take effect when writing data.

If the opening mode is not one of the above letters, the method will raise error -8085.

When the timeout parameter is -1, the connection waits forever.

The method raises error -8084 if the channel cannot be opened.


CALL ch.openClientSocket( "localhost", 80, "u", 5 )

For a complete example, see Example 4: Communicating with an HTTP server.