These mechanically follow the pleasantly transparent 'hello world'-ish examples in http://www.yesodweb.com/blog/2014/03/network-conduit-async which mix networking ABCs with elementary concurrency and conduitry (here, pipe-istry).
Apart from pipes-network and async we need the pleasant
word8 library. They use lens-family for the lens operations.
The pipes variants follow Michael S's text in this order:
Examples/ServerToUpper.hs- a server on 4000 that sends back input sent e.g. with telnet upper-cased or 'angry'
Examples/ServerDoubler.hs- a server on 4001 that sends back
input doubled,
Char8byChar8
- a server on 4001 that sends back
input doubled,
Examples/ClientToUpper.hs- a client through which the user interacts directly to the "angry" server
Examples/ClientPipeline.hs- a client that sends material to the "angry" server and the doubling server and returns it to the user
Examples/ProxyToUpper.hs- a proxy on 4002 that sends input to the angry server on 4000
Examples/ProxyAuth.hs- a proxy on 4003 that asks for demands authorization before condescending to send user input to the angry server on 4000
The following remarks will require that eight
instances of a terminal all be opened in the main
directory of the repository; if you like you can
cabal install from the main directory, and a
crude option parser will make the examples usable with
one executable:
$ pipes-network-tcp-examples --help
Usage: pipes-network-tcp-examples COMMAND
Available options:
-h,--help Show this help text
Available commands:
ClientPipeline
ClientToUpper
ProxyAuth
ProxyToUpper
ServePipes
ServerDouble
ServerToUpper
Since most examples use the uppercasing service, which looks like this:
main :: IO ()
main = do putStrLn "Opening upper-casing service on 4000"
serve (Host "127.0.0.1") "4000" $ \(client,_) ->
runEffect $ fromSocket client 4096
>-> Bytes.map toUpper
>-> toSocket client
we start it in one terminal:
term1$ runhaskell Examples/ServerToUpper.hs
Opening upper-casing service on 4000
or:
term1$ pipes-network-tcp-examples ServerToUpper
Opening upper-casing service on 4000
then in another terminal we can write
term2$ telnet localhost 4000
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
hello -- <-- our input
HELLO
...
or we can scrap telnet and use a dedicated Haskell client, which reads like this:
main = connect "127.0.0.1" "4000" $ \(connectionSocket,_) -> do
let act1 = runEffect $ PB.stdin >-> toSocket connectionSocket
act2 = runEffect $ fromSocket connectionSocket 4096 >-> PB.stdout
concurrently act1 act2
return ()
thus:
term3$ runhaskell Examples/ClientToUpper.hs # or pipes-network-tcp-examples ClientToUpper
el pueblo unido jamas sera vencido! -- our input
EL PUEBLO UNIDO JAMAS SERA VENCIDO!
el pueblo unido jamas sera vencido!
EL PUEBLO UNIDO JAMAS SERA VENCIDO!
...
In a flurry of terminal-openings we can also start up the doubling service
term4$ runhaskell Examples/ServerDouble.hs # or pipes-network-tcp-examples ServerDouble
then elsewhere
term5$ telnet localhost 4001
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
hello
hheelllloo
But let's try the Haskell client that interacts with 4000 and 4001 together, i.e.:
main = connect "127.0.0.1" "4000" $ \(socket1,_) ->
connect "127.0.0.1" "4001" $ \(socket2,_) ->
do let act1 = runEffect $ PB.stdin >-> toSocket socket1
act2 = runEffect $ fromSocket socket1 4096 >-> toSocket socket2
act3 = runEffect $ fromSocket socket2 4096 >-> PB.stdout
runConcurrently $ Concurrently act1 *>
Concurrently act2 *>
Concurrently act3
(note the use of the Applicative instance for Concurrently from the
async library), thus:
term6$ runhaskell Examples/ClientPipeline.hs # or pipes-network-tcp-examples ClientPipeline
hello
HHEELLLLOO
Don't tell the children they can access the 'angry' server directly on localhost 4000; we will demand authorization on 4003
term7$ runhaskell Examples/ProxyAuth.hs
or
term7$ pipes-network-tcp-examples ProxyAuth
which then elsewhere permits
term8$ telnet localhost 4003
Trying 127.0.0.1...
Connected to localhost.
Escape character is '^]'.
Username: spaceballs
Password: 12345
Successfully authenticated.
joy to the world!
JOY TO THE WORLD!
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