diff --git a/build.sh b/build.sh
index 85e6ceb..90097b4 100755
--- a/build.sh
+++ b/build.sh
@@ -9,14 +9,8 @@ fi
 # run cmake on ngtcp2 sources
 cmake -S "${root}/sources" -B "${root}/build"
 
-# C includes
-cat "${root}/includes.nim" > "${root}/ngtcp2.nim"
-
-# dividing line
-echo >> "${root}/ngtcp2.nim"
-
-# socket definitions
-cat "${root}/sockets.nim" >> "${root}/ngtcp2.nim"
+# add prelude
+cat "${root}/prelude.nim" > "${root}/ngtcp2.nim"
 
 # dividing line
 echo >> "${root}/ngtcp2.nim"
diff --git a/ngtcp2.nim b/ngtcp2.nim
index b35d932..9a6b022 100644
--- a/ngtcp2.nim
+++ b/ngtcp2.nim
@@ -1,112 +1,18 @@
-# C include directories
-
 import os
 import strformat
+import ngtcp2/sockets
 
+# Socket definitions
+export sockets
+
+# C include directories
 const root = currentSourcePath.parentDir
 const sourceInclude = root/"sources"/"lib"/"includes"
 const buildInclude = root/"build"/"lib"/"includes"
 
 {.passC: fmt"-I{sourceInclude} -I{buildInclude}".}
 
-# Import socket definitions from system
-import nativesockets
-export Port
-
-when defined(windows):
-  {.passL: "-lws2_32".}
-  {.
-    pragma: import_in_addr,
-    importc: "struct in_addr",
-    header: "<winsock2.h>"
-  .}
-  {.
-    pragma: import_in6_addr,
-    importc: "struct in6_addr",
-    header: "<in6addr.h>"
-  .}
-  {.
-    pragma: import_sockaddr,
-    importc: "struct sockaddr",
-    header: "<ws2tcpip.h>"
-  .}
-  {.
-    pragma: import_sockaddr_in,
-    importc: "struct sockaddr_in",
-    header: "<ws2tcpip.h>"
-  .}
-  {.
-    pragma: import_sockaddr_in6,
-    importc: "struct sockaddr_in6",
-    header: "<ws2tcpip.h>"
-  .}
-  {.
-    pragma: import_sockaddr_storage,
-    importc: "struct sockaddr_storage",
-    header: "<ws2tcpip.h>"
-  .}
-else:
-  {.
-    pragma: import_in_addr,
-    importc: "struct in_addr",
-    header: "<netinet/in.h>"
-  .}
-  {.
-    pragma: import_in6_addr,
-    importc: "struct in6_addr",
-    header: "<netinet/in.h>"
-  .}
-  {.
-    pragma: import_sockaddr
-    importc: "struct sockaddr",
-    header: "<sys/socket.h>"
-  .}
-  {.
-    pragma: import_sockaddr_in,
-    importc: "struct sockaddr_in",
-    header: "<netinet/in.h>"
-  .}
-  {.
-    pragma: import_sockaddr_in6,
-    importc: "struct sockaddr_in6",
-    header: "<netinet/in.h>"
-  .}
-  {.
-    pragma: import_sockaddr_storage,
-    importc: "struct sockaddr_storage",
-    header: "<sys/socket.h>"
-  .}
-
-type
-  AddressFamily* {.size: sizeof(uint16).} = enum
-    AF_INET = nativesockets.AF_INET
-    AF_INET6 = nativesockets.AF_INET6
-  in_addr* {.import_in_addr.} = object
-    s_addr*: uint32
-  in6_addr* {.import_in6_addr.} = object
-    s6_addr*: array[16, uint8]
-  sockaddr_storage* {.import_sockaddr_storage.} = object
-  sockaddr_in* {.import_sockaddr_in.} = object
-    sin_family*: AddressFamily
-    sin_port*: Port
-    sin_addr*: in_addr
-    sin_zero*: array[8, char]
-  sockaddr_in6* {.import_sockaddr_in6.} = object
-    sin6_family*: AddressFamily
-    sin6_port*: Port
-    sin6_flowinfo*: uint32
-    sin6_address*: in6_addr
-    sin6_scopy_id*: uint32
-  sockaddr* {.import_sockaddr.} = object
-    sa_family*: AddressFamily
-    sa_data*: array[14, char]
-  SocketAddress* {.union.} = object
-    address*: sockaddr
-    ipv4*: sockaddr_in
-    ipv6*: sockaddr_in6
-    storage*: sockaddr_storage
-
-# Generated @ 2020-09-10T16:49:03+02:00
+# Generated @ 2020-09-10T17:06:23+02:00
 # Command line:
 #   /home/user/.nimble/pkgs/nimterop-0.6.11/nimterop/toast --compile=./sources/lib/ngtcp2_acktr.c --compile=./sources/lib/ngtcp2_addr.c --compile=./sources/lib/ngtcp2_buf.c --compile=./sources/lib/ngtcp2_cc.c --compile=./sources/lib/ngtcp2_cid.c --compile=./sources/lib/ngtcp2_conn.c --compile=./sources/lib/ngtcp2_conv.c --compile=./sources/lib/ngtcp2_crypto.c --compile=./sources/lib/ngtcp2_err.c --compile=./sources/lib/ngtcp2_gaptr.c --compile=./sources/lib/ngtcp2_idtr.c --compile=./sources/lib/ngtcp2_ksl.c --compile=./sources/lib/ngtcp2_log.c --compile=./sources/lib/ngtcp2_map.c --compile=./sources/lib/ngtcp2_mem.c --compile=./sources/lib/ngtcp2_path.c --compile=./sources/lib/ngtcp2_pkt.c --compile=./sources/lib/ngtcp2_ppe.c --compile=./sources/lib/ngtcp2_pq.c --compile=./sources/lib/ngtcp2_pv.c --compile=./sources/lib/ngtcp2_qlog.c --compile=./sources/lib/ngtcp2_range.c --compile=./sources/lib/ngtcp2_ringbuf.c --compile=./sources/lib/ngtcp2_rob.c --compile=./sources/lib/ngtcp2_rst.c --compile=./sources/lib/ngtcp2_rtb.c --compile=./sources/lib/ngtcp2_str.c --compile=./sources/lib/ngtcp2_strm.c --compile=./sources/lib/ngtcp2_vec.c --compile=./sources/lib/ngtcp2_version.c --pnim --preprocess --noHeader --defines=NGTCP2_STATICLIB --includeDirs=./sources/lib/includes --includeDirs=./build/lib/includes ./sources/lib/includes/ngtcp2/ngtcp2.h
 
diff --git a/ngtcp2.nimble b/ngtcp2.nimble
index 2898089..3189341 100644
--- a/ngtcp2.nimble
+++ b/ngtcp2.nimble
@@ -3,7 +3,7 @@ version = "0.1.0"
 author = "Status Research & Development GmbH"
 description = "Nim wrapper around the ngtcp2 library"
 license = "MIT"
-installDirs = @["sources", "build"]
+installDirs = @["sources", "build", "ngtcp2"]
 installFiles = @["ngtcp2.nim"]
 
 requires "nim >= 1.2.6"
diff --git a/sockets.nim b/ngtcp2/sockets.nim
similarity index 100%
rename from sockets.nim
rename to ngtcp2/sockets.nim
diff --git a/includes.nim b/prelude.nim
similarity index 81%
rename from includes.nim
rename to prelude.nim
index d1d0897..7e7ad4f 100644
--- a/includes.nim
+++ b/prelude.nim
@@ -1,8 +1,11 @@
-# C include directories
-
 import os
 import strformat
+import ngtcp2/sockets
 
+# Socket definitions
+export sockets
+
+# C include directories
 const root = currentSourcePath.parentDir
 const sourceInclude = root/"sources"/"lib"/"includes"
 const buildInclude = root/"build"/"lib"/"includes"
diff --git a/tests/testNgtcp2.nim b/tests/testNgtcp2.nim
index dd3416d..c1f37a8 100644
--- a/tests/testNgtcp2.nim
+++ b/tests/testNgtcp2.nim
@@ -6,20 +6,3 @@ test "default settings":
   ngtcp2_settings_default(addr settings)
   check settings.transport_params.max_udp_payload_size > 0
   check settings.transport_params.active_connection_id_limit > 0
-
-test "BSD socket addresses":
-  check sizeof(in_addr) == 4
-  check sizeof(in6_addr) == 16
-  check sizeof(sockaddr) < sizeof(sockaddr_storage)
-  check sizeof(sockaddr_in) < sizeof(sockaddr_storage)
-  check sizeof(sockaddr_in6) < sizeof(sockaddr_storage)
-  check sizeof(sockaddr_in.sin_family) == 2
-  check sizeof(sockaddr_in.sin_port) == 2
-  check cast[uint16](AF_INET) == 2
-
-test "SocketAddress union":
-  var address: SocketAddress
-  check sizeof(address) == sizeof(sockaddr_storage)
-  address.address.sa_family = AF_INET
-  check address.ipv4.sin_family == AF_INET
-  check address.ipv6.sin6_family == AF_INET
diff --git a/tests/testSockets.nim b/tests/testSockets.nim
new file mode 100644
index 0000000..83ee8df
--- /dev/null
+++ b/tests/testSockets.nim
@@ -0,0 +1,19 @@
+import unittest
+import ngtcp2
+
+test "BSD socket addresses":
+  check sizeof(in_addr) == 4
+  check sizeof(in6_addr) == 16
+  check sizeof(sockaddr) < sizeof(sockaddr_storage)
+  check sizeof(sockaddr_in) < sizeof(sockaddr_storage)
+  check sizeof(sockaddr_in6) < sizeof(sockaddr_storage)
+  check sizeof(sockaddr_in.sin_family) == 2
+  check sizeof(sockaddr_in.sin_port) == 2
+  check cast[uint16](AF_INET) == 2
+
+test "SocketAddress union":
+  var address: SocketAddress
+  check sizeof(address) == sizeof(sockaddr_storage)
+  address.address.sa_family = AF_INET
+  check address.ipv4.sin_family == AF_INET
+  check address.ipv6.sin6_family == AF_INET