OPENHOST

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The _OPENHOST function opens a Host which listens for new connections and returns a Host status handle.


Syntax

host_handle = _OPENHOST("TCP/IP:8080")


Description

  • Creates an ILLEGAL FUNCTION CALL if called with a string argument of the wrong syntax.
  • The port used in the syntax example is 8080.
  • Valid handle values are usually negative number values.
  • If the syntax is correct but they fail to begin/connect a handle of 0 is returned.
  • Always check if the handle returned is 0 (failed) before continuing.
  • CLOSE host_handle closes the host. A failed handle value of 0 does not need to be closed.


Examples

Example: Chat program that attempts to connect as a Client. If not it attempts to become the Host.

PRINT "Mini Messenger" LOCATE , , 1 ' display the print cursor for INKEY$ client = _OPENCLIENT("TCP/IP:7319:localhost") ' Attempt to connect to local host as a client IF client THEN PRINT "[connected to " + _CONNECTIONADDRESS(client) + "]" _TITLE "Client - Mini Messenger" INPUT "Enter your name: ", myname$ PRINT #client, myname$ + " connected!" DO GetMessage client SendMessage myname$, mymessage$, client ' display current input on screen _DELAY 0.01 ' reduce CPU usage LOOP ELSE ' "if client" alternative to open a new Host PRINT "[No existing host found]" host = _OPENHOST("TCP/IP:7319") ' no host found, so begin new host IF host THEN _TITLE "Host - Mini Messenger" PRINT "[Beginning new host chat session!]" DIM Users(1 to 1000) ' array to hold other client info numclients = 0 client = _OPENCLIENT("TCP/IP:7319:localhost") IF client = 0 THEN PRINT "ERROR: could not attach host's personal client to host!" INPUT "Enter your name:", myname$ PRINT #client, myname$ + " connected!" PRINT "[Chat session active!]" DO ' host main loop newclient = _OPENCONNECTION(host) ' receive any new connection IF newclient THEN numclients = numclients + 1 Users(numclients) = newclient PRINT #Users(numclients),"Welcome!" END IF FOR i = 1 TO numclients ' distribute incoming messages to all clients IF Users(i) THEN INPUT #Users(i), message$ IF message$ <> "" THEN FOR p = 1 TO numclients IF Users(p) THEN PRINT #Users(p), message$ NEXT p END IF END IF NEXT i GetMessage client ' allow host to get messages and chat also SendMessage myname$, mymessage$, client _DELAY 0.01 ' reduce CPU usage LOOP END IF ' host PRINT "ERROR: Could not begin new host!" END IF ' if client from start SLEEP SYSTEM '.................... END OF MAIN PROGRAM ................ SUB GetMessage (client) ' get & display any new message INPUT #client, newmessage$ IF newmessage$ <> "" THEN VIEW PRINT 1 TO 23 LOCATE 23,1 PRINT newmessage$ VIEW PRINT 1 TO 24 END IF END SUB SUB SendMessage (myname$, mymessage$, client) ' simple input handler k$ = INKEY$ IF LEN(k$) THEN IF k$ = CHR$(8) AND LEN(mymessage$) <> 0 THEN mymessage$ = LEFT$(mymessage$, LEN(mymessage$) - 1) ELSE IF LEN(k$) = 1 AND ASC(k$) >= 32 THEN mymessage$ = mymessage$ + k$ END IF END IF LOCATE 24, 1: PRINT SPACE$(80); ' erase previous message displayed LOCATE 24, 1: PRINT myname$ + ": ";mymessage$; IF k$ = CHR$(13) THEN ' [Enter] sends the message IF mymessage$ = "" THEN SYSTEM ' [Enter] with no message ends program PRINT #client, myname$ + ": " + mymessage$ mymessage$ = "" END IF IF k$ = CHR$(27) THEN SYSTEM ' [Esc] key ends program END SUB

Mini Messenger [No existing host found] [Beginning new host chat session!] Enter your name:_

Explanation: The SendMessage SUB program controls the program exit unless both Client and Host fail. Entering no message and hitting [Enter] or pressing the [Esc]] key closes the program. Both SUB programs allow a Client or Host to communicate with others simply. INPUT # is used to read messages and PRINT # is used to send messages. The client handle value is used as the port number. Keep in mind that this is just an example. A lot could be added like recording IP addresses!

To manage the users array, see the _CONNECTED page example.


See also




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