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Haskell Distributed Project

This repository holds an implementation of Cloud Haskell based on the work of Jeff Epstein, Andrew Black, and Simon Peyton-Jones.

At present, this repository hosts two packages:

  • distributed-process
  • network-transport

For more detailed information about the interfaces provided by these packages, please refer to the distributed-process repository wiki.


Examples of the transport layer at work can be found in the /examples folder.


The DemoTransport.hs file contains a number of different functions named demo#. These functions demonstrate the use of the Network.Transport module.

To try them out, launch ghci, including the appropriate sources:

ghci -idistributed-process/src -inetwork-transport/src examples/DemoTransport.hs

The first demo, demo0 yields the following output when run with the TCP transport:

*DemoTransport> tcp >>= demo0
logServer: [Chunk "hello 1" Empty]
logServer: [Chunk "hello 2" Empty]
logServer: [Chunk "hello 3" Empty]
logServer: [Chunk "hello 4" Empty]
logServer: [Chunk "hello 5" Empty]
logServer: [Chunk "hello 6" Empty]
logServer: [Chunk "hello 7" Empty]
logServer: [Chunk "hello 8" Empty]
logServer: [Chunk "hello 9" Empty]
logServer: [Chunk "hello 10" Empty]

See the source code for more details.


The DemoProcess.hs file shows a very basic example of how to use the Control.Distributed.Process module in conjunction with Network.Transport.TCP. This is demonstrated using the demo1 function:

ghci -idistributed-process/src -inetwork-transport/src examples/DemoProcess.hs

The output of the example is as follows:

*DemoProcess> demo1
"Starting node"
"Starting process"
1: jim1 says: hi there
2: bob1 says: hi there
3: jim1 says: bye
4: bob1 says: bye


The DemoTCP.hs file demonstrates how a master can be connected to slaves using the transport layer over TCP. This example should be compiled in the usual fashion:

ghc --make -idistributed-process/src -inetwork-transport/src examples/DemoTCP.hs

After compiling, the following will initialize a new master that waits for two clients to connect on the local machine:

./examples/DemoTCP 8080 sourceAddrFile 2

Following this, two slaves should be created that will connect to the master:

./examples/DemoTCP 8081 sourceAddrFile
./examples/DemoTCP 8082 sourceAddrFile

Once the connection is established, the slaves will provide the master with their SourceAddr. The master then decodes this, and sends a message back. After processing this message, the slaves respond to the master, which then outputs some data.


The Transport.TCP backend uses Network.ByteString.Lazy as its underlying protocol, so we produce a benchmark that compares it directly with this. Furthermore, the Data.Binary package is used for converting values to ByteStrings for transmission.

The benchmarking is performed on the client side using criterion: the server must be set up before benching is performed.


This benchmark measures how quickly a sequence of ping/pong messages are sent between a server and client. Full details can be found in:



This benchmark measures how quickly a number of bytes can be sent from a client to a server. Full details can be found in the following files: