diff --git a/Network/Run/TCP.hs b/Network/Run/TCP.hs
--- a/Network/Run/TCP.hs
+++ b/Network/Run/TCP.hs
@@ -15,7 +15,7 @@
 import Network.Run.Core
 
 -- | Running a TCP client with a connected socket.
-runTCPClient :: String -> String -> (Socket -> IO a) -> IO a
+runTCPClient :: HostName -> ServiceName -> (Socket -> IO a) -> IO a
 runTCPClient host port client = withSocketsDo $ do
     addr <- resolve Stream (Just host) port False
 #if MIN_VERSION_network(3,1,1)
diff --git a/Network/Run/UDP.hs b/Network/Run/UDP.hs
--- a/Network/Run/UDP.hs
+++ b/Network/Run/UDP.hs
@@ -13,7 +13,7 @@
 --   The client action takes a socket and
 --   server's socket address.
 --   They should be used with 'sendTo'.
-runUDPClient :: String -> String -> (Socket -> SockAddr -> IO a) -> IO a
+runUDPClient :: HostName -> ServiceName -> (Socket -> SockAddr -> IO a) -> IO a
 runUDPClient host port client = withSocketsDo $ do
     addr <- resolve Datagram (Just host) port False
     let sockAddr = addrAddress addr
diff --git a/network-run.cabal b/network-run.cabal
--- a/network-run.cabal
+++ b/network-run.cabal
@@ -1,5 +1,5 @@
 name:                network-run
-version:             0.2.0
+version:             0.2.1
 synopsis:            Simple network runner library
 description:         Simple functions to run network clients and servers.
 -- bug-reports: