You may have figured this out by now, but according to the docs, the error
is correct: PortNumber exposes no constructor at all. Instead, it has a Num
instance; you should be able to just use the literal 7200 there.
This strikes me as a highly questionable decision on the part of the module
authors, but it is at least convenient.
On Wed, Aug 14, 2019, 10:59 AM Jeff C. Britton
I have just installed Haskell using Stack on Windows.
I wanted to try and write some code to do network programming with TCP/IP.
I found a simple example on Stack Overflow to start me off.
I’m having some problems with PortNumber and deprecated warnings.
I don't know how to modify the code to be deprecation free.
stack install network – installed version 2.8.0.1
-------------------------
package.yaml
network >= 2.8.0.1
---------------------------
The following code gives a deprecation warning, but ultimately my sample compiles and runs.
import qualified Network
import qualified Network.Socket
main = Network.withSocketsDo $ do
handle <- Network.connectTo "192.168.1.2" (Network.PortNumber 7200)
talk handle `finally` hClose handle
D:\work\hsSocket\app\Main.hs:14:46: warning: [-Wdeprecations]
In the use of data constructor `PortNumber'
(imported from Network):
Deprecated: "The high level Network interface is no longer supported. Please use Network.Socket."
-----------------------------------------
So, now I try and use Network.Socket as the warning indicates.
main = Network.withSocketsDo $ do
handle <- Network.connectTo "192.168.1.2" (Network.Socket.PortNumber 7200)
talk handle `finally` hClose handle
D:\work\hsSocket\app\Main.hs:15:46: error:
Not in scope: data constructor `Network.Socket.PortNumber'
Module `Network.Socket' does not export `PortNumber'.
|
15 | handle <- Network.connectTo "192.168.1.2" (Network.Socket.PortNumber 7200)
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