TCPConnectionGetCharacters

function

Library: TCP/IP client and server support (OMTCP legacy, OmniMark versions 4 - 6.0.1)
Include: omtcp.xin

Returns: Characters read from the TCP connection.

Declaration

define external stream function TCPConnectionGetCharacters
    value       TCPConnection this-TCPConnection
    size        value         integer minimum-read-length      optional
    variable-to value         integer maximum-read-length      optional
    timeout     value         integer timeout-in-milliseconds optional
 as "TCPConnectionGetCharacters"

Purpose

This function reads characters received from a source on the TCP connection object.

There are four combinations for specifying the size and variable-to values, as follows:

If neither is specified, then TCPConnectionGetCharacters returns as many characters as it has available, as long as it has at least one character. It will wait (only for as long as the timeout value if one is specified) for at least one character, only if it has no characters to return.
If only the size value is specified, TCPConnectionGetCharacters reads and returns exactly minimum-read-length characters. If a timeout value is specified and is exceeded, it will return immediately with the (zero or more) characters it has available. It will also set the TCP connection to be in error.
If only the variable-to value is specified, then TCPConnectionGetCharacters reads as many characters as it has available, as if neither size nor variable-to were specified, except that if it has more than maximum-read-length available, it will only return maximum-read-length and will save any remaining characters for a subsequent read.
If both the size and variable-to values are specified, then TCPConnectionGetCharacters reads at least minimum-read-length characters, but will return up to maximum-read-length characters, if it has them available. Like the size value only case, it can timeout in reading the first minimum-read-length characters, but will not do so once that many have been read. It is an error for the size value to be greater than the variable-to value.

If the passed TCP connection object is closed or was never connected, then this function returns zero characters. At the same time, it sets the TCP connection to be in error. If an error is encountered during reading, either zero characters or those already read (if any) are returned, as seems appropriate, and the TCP connection object is set to be in error.

Note that difficulties inherent in deriving multiple sources from a connection apply equally to using TCPConnectionGetCharacters when a TCPConnectionGetSource derived source is also active. Note, however, that sequential uses of TCPConnectionGetCharacters are allowed. It is also guaranteed that a TCPConnectionGetCharacters will only ever read the characters it returns from a source. Any following characters are available to the next TCPConnectionGetSource, TCPConnectionGetCharacters, or TCPConnectionGetLine.

Any attempt to do a TCPConnectionGetCharacters when the associated TCP connection has been closed using TCPConnectionClose is in error, and will set the TCP connection to be in error.

Any attempt to do a TCPConnectionGetCharacters when there is already an active source derived from TCPConnectionGetSource is not allowed and will result in an OmniMark external function exception.

Arguments:

"this-TCPConnection" is an OMX component of type TCPConnection.
"minimum-read-length" is the minimum number of characters TCPConnectionGetCharacters will read.
"maximum-read-length" is the maximum number of characters TCPConnectionGetCharacters will read.
"timeout-in-milliseconds" is the length of time the function will run for before terminating automatically.

Example

  local TCPConnection TCP-Conn
  
  set TCP-Conn to TCPConnectionOpen on "localhost" at 5300
  
  repeat 
     exit unless TCPConnectionIsConnected TCP-Conn
     output TCPConnectionGetCharacters TCP-Conn
  again