diff --git a/punchd.nim b/punchd.nim
index cd716b7..a3578e7 100644
--- a/punchd.nim
+++ b/punchd.nim
@@ -1,12 +1,13 @@
-import asyncdispatch, asyncnet, os, strformat, strutils
 from nativesockets import Domain, SockType, Protocol
+from net import IpAddress, Port, `$`, `==`, parseIpAddress
+from sequtils import filter
+import asyncdispatch, asyncnet, os, strformat, strutils
 import asyncutils
 import message
+import options
 import tables
-import tcp_syni_initiator
-import tcp_syni_responder
-import tcp_nutss_initiator
-import tcp_nutss_responder
+import tcp_syni
+import tcp_nutss
 
 from strutils import format, join
 from nativesockets import setSockOptInt
@@ -14,8 +15,8 @@ from nativesockets import setSockOptInt
 type
   Punchd = ref object
     unixSocket: AsyncSocket
-    initiators: Table[string, Initiator]
-    responders: Table[string, Responder]
+    punchers: Table[string, Puncher]
+    attempts: seq[Attempt]
 
   Sigint = object of CatchableError
 
@@ -30,23 +31,87 @@ proc sendToClient(unixSock: AsyncSocket, msg: string,
     let unixFd = unixSock.getFd.AsyncFD
     await unixFd.asyncSendMsg(msg, cmsgs)
 
+proc findAttemptsByLocalAddr(punchd: Punchd, srcIp: IpAddress,
+                             srcPort: Port): seq[Attempt] =
+  proc matchesLocalAddr(a: Attempt): bool =
+    a.srcIp == srcIp and a.srcPort == srcPort
+  punchd.attempts.filter(matchesLocalAddr)
+
+proc acceptConnections(punchd: Punchd, ip: IpAddress, port: Port,
+                       protocol: Protocol) {.async.} =
+  var sockType: SockType
+  case protocol:
+  of IPPROTO_TCP:
+    sockType = SOCK_STREAM
+  of IPPROTO_UDP:
+    sockType = SOCK_DGRAM
+  else:
+    assert(false, "can only accept TCP or UDP connections")
+  let sock = newAsyncSocket(sockType = sockType, protocol = protocol)
+  sock.bindAddr(port, $ip)
+  sock.listen()
+  while true:
+    let acceptFuture = sock.accept()
+    await acceptFuture or sleepAsync(Timeout)
+    if acceptFuture.finished():
+      let peer = acceptFuture.read()
+      let (peerAddr, peerPort) = peer.getPeerAddr()
+      let peerIp = parseIpAddress(peerAddr)
+      let query = Attempt(srcIp: ip, srcPort: port, dstIp: peerIp,
+                          dstPorts: @[peerPort])
+      let i = punchd.attempts.find(query)
+      if i == -1:
+        echo "Accepted connection, but no attempt found. Discarding."
+        peer.close()
+        continue
+      else:
+        let acceptFuture = punchd.attempts[i].acceptFuture.get()
+        acceptFuture.complete(peer)
+    let localAddrMatches = punchd.findAttemptsByLocalAddr(ip, port)
+    if localAddrMatches.len() <= 1:
+      break
+  sock.close()
+
+proc addAttempt(punchd: Punchd, attempt: Attempt, puncher: Puncher) =
+  let localAddrMatches = punchd.findAttemptsByLocalAddr(attempt.srcIp,
+                                                        attempt.srcPort)
+  punchd.attempts.add(attempt)
+  if localAddrMatches.len() == 0:
+    if attempt.acceptFuture.isSome():
+      asyncCheck punchd.acceptConnections(attempt.srcIp, attempt.srcPort,
+                                          puncher.getProtocol())
+  elif localAddrMatches.contains(attempt):
+    raise newException(PunchHoleError,
+                       "hole punching for given parameters already active")
+
+proc removeAttempt(punchd: Punchd, attempt: Attempt) =
+  punchd.attempts.del(punchd.attempts.find(attempt))
+
 proc handleRequest(punchd: Punchd, line: string,
                    unixSock: AsyncSocket) {.async.} =
   var id: string
   var sock: AsyncSocket
+  var attempt: Attempt
   try:
     let args = line.parseArgs(4)
     id = args[1]
+    let puncher = punchd.punchers[args[2]]
 
     case args[0]:
     of "initiate":
+      attempt = puncher.parseInitiateRequest(args[3])
+      punchd.addAttempt(attempt, puncher)
       proc progress(extraArgs: string) {.async.} =
         let msg = &"progress|{id}|{args[2]}|{args[3]}|{extraArgs}\n"
         await sendToClient(unixSock, msg)
-      sock = await punchd.initiators[args[2]].initiate(args[3], progress)
+      sock = await puncher.initiate(attempt, progress)
+      punchd.removeAttempt(attempt)
 
     of "respond":
-      sock = await punchd.responders[args[2]].respond(args[3])
+      attempt = puncher.parseRespondRequest(args[3])
+      punchd.addAttempt(attempt, puncher)
+      sock = await puncher.respond(attempt)
+      punchd.removeAttempt(attempt)
 
     else:
       raise newException(ValueError, "invalid request")
@@ -55,6 +120,7 @@ proc handleRequest(punchd: Punchd, line: string,
     sock.close()
 
   except PunchHoleError as e:
+    punchd.removeAttempt(attempt)
     await sendToClient(unixSock, &"error|{id}|{e.msg}\n")
   except KeyError, ValueError:
     unixSock.close
@@ -84,19 +150,15 @@ proc main() =
                      {fpUserRead, fpUserWrite, fpGroupRead, fpGroupWrite,
                       fpOthersRead, fpOthersWrite})
   let punchd = Punchd(unixSocket: unixSocket)
-  punchd.initiators["tcp-syni"] = initTcpSyniInitiator()
-  punchd.initiators["tcp-nutss"] = initTcpNutssInitiator()
-  punchd.responders["tcp-syni"] = initTcpSyniResponder()
-  punchd.responders["tcp-nutss"] = initTcpNutssResponder()
+  punchd.punchers["tcp-syni"] = initTcpSyniPuncher()
+  punchd.punchers["tcp-nutss"] = initTcpNutssPuncher()
   asyncCheck handleUsers(punchd)
   try:
     runForever()
 
   except Sigint:
-    for i in punchd.initiators.values:
-      waitFor i.cleanup()
-    for r in punchd.responders.values:
-      waitFor r.cleanup()
+    while punchd.attempts.len() != 0:
+      waitFor punchd.attempts.pop().cleanup()
     punchd.unixSocket.close()
     removeFile(PunchdSocket)
 
diff --git a/puncher.nim b/puncher.nim
index 4a41201..a16534e 100644
--- a/puncher.nim
+++ b/puncher.nim
@@ -1,54 +1,97 @@
-import asyncdispatch, asyncnet, strformat
+import asyncdispatch, asyncnet, strformat, options
+from nativesockets import Protocol
 from net import IpAddress, Port, `$`, `==`
 from sequtils import any
 import asyncutils
 
 type
   Attempt* = ref object of RootObj
+    ## A hole punching attempt.
+    ##
+    ## It is created by parsing the arguments of a request in either
+    ## ``parseInitiateRequest`` or ``parseRespondRequest`` and must not be
+    ## modified afterwards. By inclduing ``some(acceptFuture)``, the puncher
+    ## tells the caller to accept connections at the local IP address and
+    ## port ``srcPort`` before calling ``initiate``. The desired transport
+    ## protocol can be obtained by calling ``getProcotol``. The puncher expects
+    ## the caller to complete the future when a connections from
+    ## ``dstIp``:``dstPort`` has been accepted.
     srcIp*: IpAddress
     srcPort*: Port
     dstIp*: IpAddress
     dstPorts*: seq[Port]
+    acceptFuture*: Option[Future[AsyncSocket]]
 
   Puncher* = ref object of RootObj
-    attempts*: seq[Attempt]
-
-  Initiator* = ref object of Puncher
-
-  Responder* = ref object of Puncher
+    ## A hole puncher.
 
   PunchHoleError* = object of ValueError
+    attempt: Attempt
+    ## An exception indicating that the contained ``attempt`` has failed.
 
   PunchProgressCb* = proc(extraArgs: string) {.async.}
+    ## A callback to allow a puncher report progress.
+    ##
+    ## When called a status message of type ``progress``, including the given
+    ## ``extraArgs`` has to be sent to the application.
 
 const Timeout* = 3000
 
-proc findAttempt*(puncher: Puncher, srcIp: IpAddress, srcPort: Port,
-                  dstIp: IpAddress, dstPorts: seq[Port]): int =
-  for (index, attempt) in puncher.attempts.pairs():
-    if attempt.srcIp == srcIp and attempt.srcPort == srcPort and
-       attempt.dstIp == dstIp and
-       attempt.dstPorts.any(proc (p: Port): bool = p in dstPorts):
-      return index
-  return -1
+proc `==`*(a, b: Attempt): bool =
+  ## ``==`` for hole punching attempts.
+  ##
+  ## Two hole punching attempts are considered equal if their ``srcIp``,
+  ## ``srcPort`` and ``dstIp`` are equal and their ``dstPorts`` overlap.
+  a.srcIp == b.srcIp and a.srcPort == b.srcPort and a.dstIp == b.dstIp and
+  a.dstPorts.any(proc (p: Port): bool = p in b.dstPorts)
 
-proc findAttemptsByLocalAddr*(puncher: Puncher, address: IpAddress,
-                              port: Port): seq[Attempt] =
-  for attempt in puncher.attempts:
-    if attempt.srcIp == address and attempt.srcPort == port:
-      result.add(attempt)
+method cleanup*(attempt: Attempt): Future[void] {.base, async.} =
+  ## Cleans up when an attempt finished (either successful or not).
+  ##
+  ## Does nothing. Override for custom attempt types.
+  discard
 
-method cleanup*(puncher: Puncher): Future[void] {.base, async.} =
-  block: # workaround for https://github.com/nim-lang/Nim/issues/12530
-    raise newException(CatchableError, "Method without implementation override")
+method getProtocol*(puncher: Puncher): Protocol {.base.} =
+  ## Returns the transport protocol the puncher employs. 
+  raise newException(CatchableError, "Method without implementation override")
 
-method initiate*(puncher: Initiator, args: string, progress: PunchProgressCb):
+method parseInitiateRequest*(puncher: Puncher, args: string): Attempt {.base.} =
+  ## Creates a new hole punching attempt by parsing arguments of an ``initiate``
+  ## request.
+  ##
+  ## ``args`` has to be the arguments after the ``TECHNIQUE`` field, i.e.
+  ## ``IP_FROM|PORTS_FROM|IP_TO|PORTS_TO``. My throw a ``ValueError`` if
+  ## ``args`` is invalid.
+  raise newException(CatchableError, "Method without implementation override")
+
+method parseRespondRequest*(puncher: Puncher, args: string): Attempt {.base.} =
+  ## Creates a new hole punching attempt by parsing arguments of a ``respond``
+  ## request.
+  ##
+  ## ``args`` has to be the arguments after the ``TECHNIQUE`` field, i.e.
+  ## ``IP_FROM|PORTS_FROM|IP_TO|PORTS_TO|EXTRA_ARGS``. May throw a
+  ## ``ValueError`` if ``args`` is invalid.
+  raise newException(CatchableError, "Method without implementation override")
+
+method initiate*(puncher: Puncher, attempt: Attempt, progress: PunchProgressCb):
                 Future[AsyncSocket] {.base, async.} =
+  ## Initiate a hole punching attempt.
+  ##
+  ## ``attempt`` has to be obtained by calling ``parseInitiateRequest``.
+  ## ``progress`` will be called when the attempt has been initiated and a
+  ## status message of type ``progress`` has to be sent to the application. The
+  ## returned future contains a connected socket and will fail with a
+  ## ``PunchHoleError`` if the hole punching fails.
   block: # workaround for https://github.com/nim-lang/Nim/issues/12530
     raise newException(CatchableError, "Method without implementation override")
 
-method respond*(puncher: Responder, args: string):
+method respond*(puncher: Puncher, attempt: Attempt):
                Future[AsyncSocket] {.base, async.} =
+  ## Respond to a hole punching attempt initiated by another peer.
+  ##
+  ## ``attempt has to be obtained by calling ``parseRespondRequest``. The
+  ## returned future contains a connected socket and will fail with as
+  ## ``PunchHoleError`` if the hole punching fails.
   block: # workaround for https://github.com/nim-lang/Nim/issues/12530
     raise newException(CatchableError, "Method without implementation override")
 
diff --git a/tcp_nutss.nim b/tcp_nutss.nim
new file mode 100644
index 0000000..01c1d2a
--- /dev/null
+++ b/tcp_nutss.nim
@@ -0,0 +1,106 @@
+from nativesockets import Protocol
+from net import IpAddress, Port, `$`, `==`
+from random import randomize, rand
+import asyncdispatch, asyncnet, strformat
+import ip_packet
+import message
+import options
+import port_prediction
+import puncher
+import raw_socket
+import utils
+
+export puncher
+
+type
+  TcpNutssPuncher* = ref object of Puncher
+
+  InitiateRequest = object
+    srcIp: IpAddress
+    srcPorts: seq[Port]
+    dstIp: IpAddress
+    dstPorts: seq[Port]
+
+  RespondRequest = object
+    dstIp: IpAddress
+    dstPorts: seq[Port]
+    srcIp: IpAddress
+    srcPorts: seq[Port]
+    extraArgs: string
+
+proc injectSynPackets(attempt: Attempt) {.async.} =
+  let injectFd = setupTcpInjectingSocket()
+  for dstPort in attempt.dstPorts:
+    let synOut = IpPacket(protocol: tcp, ipAddrSrc: attempt.srcIp,
+                          ipAddrDst: attempt.dstIp, ipTTL: 2,
+                          tcpPortSrc: attempt.srcPort, tcpPortDst: dstPort,
+                          tcpSeqNumber: rand(uint32), tcpAckNumber: 0,
+                          tcpFlags: {SYN}, tcpWindowSize: 1452 * 10)
+    echo &"[{synOut.ipAddrSrc}:{synOut.tcpPortSrc} -> {synOut.ipAddrDst}:{synOut.tcpPortDst}, SEQ {synOut.tcpSeqNumber}] injecting outgoing SYN"
+    await injectFd.injectTcpPacket(synOut)
+
+proc connect(srcIp: IpAddress, srcPort: Port, dstIp: IpAddress, dstPort: Port,
+             future: Future[AsyncSocket]) {.async.} =
+  let sock = newAsyncSocket()
+  sock.setSockOpt(OptReuseAddr, true)
+  echo &"connect {srcIp}:{srcPort} -> {dstIp}:{dstPort}"
+  sock.bindAddr(srcPort, $srcIp)
+  try:
+    await sock.connect($dstIp, dstPort)
+    future.complete(sock)
+  except OSError as e:
+    echo &"connection {srcIP}:{srcPort.int} -> {dstIp}:{dstPort.int} failed: ", e.msg
+    sock.close()
+
+proc initTcpNutssPuncher*(): TcpNutssPuncher =
+  randomize()
+  TcpNutssPuncher()
+
+method getProtocol*(puncher: TcpNutssPuncher): Protocol =
+  IPPROTO_TCP
+
+method parseInitiateRequest*(puncher: TcpNutssPuncher, args: string): Attempt =
+  let parsed = parseMessage[InitiateRequest](args)
+  let localIp = getPrimaryIPAddr(parsed.dstIp)
+  let predictedDstPorts = predictPortRange(parsed.dstPorts)
+  let acceptFuture = newFuture[AsyncSocket]("parseInitiateRequest")
+  Attempt(srcIp: localIp, srcPort: parsed.srcPorts[0], dstIp: parsed.dstIp,
+          dstPorts: predictedDstPorts, acceptFuture: some(acceptFuture))
+
+method parseRespondRequest*(puncher: TcpNutssPuncher, args: string): Attempt =
+  let parsed = parseMessage[RespondRequest](args)
+  let localIp = getPrimaryIPAddr(parsed.dstIp)
+  let predictedDstPorts = predictPortRange(parsed.dstPorts)
+  Attempt(srcIp: localIp, srcPort: parsed.srcPorts[0], dstIp: parsed.dstIp,
+          dstPorts: predictedDstPorts, acceptFuture: none(Future[AsyncSocket]))
+
+method initiate*(puncher: TcpNutssPuncher, attempt: Attempt,
+                 progress: PunchProgressCb): Future[AsyncSocket] {.async.} =
+  assert(attempt.acceptFuture.isSome(), "expected attempt with acceptFuture")
+  try:
+    let acceptFuture = attempt.acceptFuture.get()
+    await injectSynPackets(attempt)
+    await progress("")
+    await acceptFuture or sleepAsync(Timeout)
+    if acceptFuture.finished():
+      result = acceptFuture.read()
+    else:
+      raise newException(PunchHoleError, "timeout")
+  except OSError as e:
+    raise newException(PunchHoleError, e.msg)
+
+method respond*(puncher: TcpNutssPuncher, attempt: Attempt):
+               Future[AsyncSocket] {.async.} =
+  assert(attempt.acceptFuture.isNone(), "expected attempt without acceptFuture")
+  try:
+    let connectFuture = newFuture[AsyncSocket]("respond")
+    for dstPort in attempt.dstPorts:
+      asyncCheck connect(attempt.srcIp, attempt.srcPort, attempt.dstIp, dstPort,
+                         connectFuture)
+    await connectFuture or sleepAsync(Timeout)
+    if connectFuture.finished():
+      result = connectFuture.read()
+    else:
+      raise newException(PunchHoleError, "timeout")
+  except OSError as e:
+    raise newException(PunchHoleError, e.msg)
diff --git a/tcp_nutss_initiator.nim b/tcp_nutss_initiator.nim
deleted file mode 100644
index 50dd5e2..0000000
--- a/tcp_nutss_initiator.nim
+++ /dev/null
@@ -1,97 +0,0 @@
-import asyncdispatch, asyncnet, strformat
-from net import IpAddress, Port, `$`, `==`, parseIpAddress
-from random import randomize, rand
-from sequtils import any
-import ip_packet
-import message
-import port_prediction
-import puncher
-import raw_socket
-import utils
-
-export Puncher, Initiator, PunchProgressCb, PunchHoleError, cleanup, initiate
-
-type
-  TNIAttempt = ref object of Attempt
-    future: Future[AsyncSocket]
-
-  TcpNutssInitiator* = ref object of Initiator
-
-  Request = object
-    srcIp: IpAddress
-    srcPorts: seq[Port]
-    dstIp: IpAddress
-    dstPorts: seq[Port]
-
-method cleanup*(puncher: TcpNutssInitiator) {.async.} =
-  discard
-
-proc initTcpNutssInitiator*(): TcpNutssInitiator =
-  randomize()
-  TcpNutssInitiator()
-
-proc injectSynPackets(attempt: TNIAttempt) {.async.} =
-  let injectFd = setupTcpInjectingSocket()
-  for dstPort in attempt.dstPorts:
-    let synOut = IpPacket(protocol: tcp, ipAddrSrc: attempt.srcIp,
-                          ipAddrDst: attempt.dstIp, ipTTL: 2,
-                          tcpPortSrc: attempt.srcPort, tcpPortDst: dstPort,
-                          tcpSeqNumber: rand(uint32), tcpAckNumber: 0,
-                          tcpFlags: {SYN}, tcpWindowSize: 1452 * 10)
-    echo &"[{synOut.ipAddrSrc}:{synOut.tcpPortSrc} -> {synOut.ipAddrDst}:{synOut.tcpPortDst}, SEQ {synOut.tcpSeqNumber}] injecting outgoing SYN"
-    await injectFd.injectTcpPacket(synOut)
-
-proc accept(puncher: TcpNutssInitiator, ip: IpAddress, port: Port) {.async.} =
-  let sock = newAsyncSocket()
-  #sock.setSockOpt(OptReuseAddr, true)
-  sock.bindAddr(port, $ip)
-  sock.listen()
-  while true:
-    let acceptFuture = sock.accept()
-    await acceptFuture or sleepAsync(Timeout)
-    if acceptFuture.finished():
-      let peer = acceptFuture.read()
-      let (peerAddr, peerPort) = peer.getPeerAddr()
-      let peerIp = parseIpAddress(peerAddr)
-      let i = puncher.findAttempt(ip, port, peerIp, @[peerPort])
-      if i == -1:
-        echo "Accepted connection, but no attempt found. Discarding."
-        peer.close()
-        continue
-      else:
-        let attempt = TNIAttempt(puncher.attempts[i])
-        attempt.future.complete(peer)
-    let attempts = puncher.findAttemptsByLocalAddr(ip, port)
-    if attempts.len() <= 1:
-      break
-  sock.close()
-
-method initiate*(puncher: TcpNutssInitiator, args: string,
-                 progressCb: PunchProgressCb): Future[AsyncSocket] {.async.} =
-  let req = parseMessage[Request](args)
-  let localIp = getPrimaryIPAddr(req.dstIp)
-  let existingAttempts = puncher.findAttemptsByLocalAddr(localIp, req.srcPorts[0])
-  if existingAttempts.len() == 0:
-    echo &"initiating connection to {req.dstIp}:{req.dstPorts[0].int}"
-    asyncCheck puncher.accept(localIp, req.srcPorts[0])
-  else:
-    for a in existingAttempts:
-      if a.dstIp == req.dstIp and
-         a.dstPorts.any(proc (p: Port): bool = p in req.dstPorts):
-        raise newException(PunchHoleError, "hole punching for given parameters already active")
-  try:
-    let attempt = TNIAttempt(srcIp: localIp, srcPort: req.srcPorts[0],
-                             dstIp: req.dstIp,
-                             dstPorts: predictPortRange(req.dstPorts),
-                             future: newFuture[AsyncSocket]("initiate"))
-    puncher.attempts.add(attempt)
-    await attempt.injectSynPackets()
-    await progressCb("")
-    await attempt.future or sleepAsync(Timeout)
-    puncher.attempts.del(puncher.attempts.find(attempt))
-    if attempt.future.finished():
-      result = attempt.future.read()
-    else:
-      raise newException(PunchHoleError, "timeout")
-  except OSError as e:
-    raise newException(PunchHoleError, e.msg)
diff --git a/tcp_nutss_responder.nim b/tcp_nutss_responder.nim
deleted file mode 100644
index aa73023..0000000
--- a/tcp_nutss_responder.nim
+++ /dev/null
@@ -1,54 +0,0 @@
-import asyncdispatch, asyncnet, strformat
-from net import IpAddress, Port, `$`, `==`
-import message
-import port_prediction
-import puncher
-import utils
-
-export Puncher, Responder, PunchHoleError, cleanup, respond
-
-type
-  TcpNutssResponder* = ref object of Responder
-
-  Request = object
-    dstIp: IpAddress
-    dstPorts: seq[Port]
-    srcIp: IpAddress
-    srcPorts: seq[Port]
-    extraData: string
-
-method cleanup*(puncher: TcpNutssResponder) {.async.} =
-  discard
-
-proc initTcpNutssResponder*(): TcpNutssResponder =
-  TcpNutssResponder()
-
-proc connect(srcIp: IpAddress, srcPort: Port, dstIp: IpAddress, dstPort: Port,
-             future: Future[AsyncSocket]) {.async.} =
-  let sock = newAsyncSocket()
-  sock.setSockOpt(OptReuseAddr, true)
-  echo &"connect {srcIp}:{srcPort} -> {dstIp}:{dstPort}"
-  sock.bindAddr(srcPort, $srcIp)
-  try:
-    await sock.connect($dstIp, dstPort)
-    future.complete(sock)
-  except OSError as e:
-    echo &"connection {srcIP}:{srcPort.int} -> {dstIp}:{dstPort.int} failed: ", e.msg
-    sock.close()
-
-method respond*(puncher: TcpNutssResponder, args: string): Future[AsyncSocket] {.async.} =
-  let req = parseMessage[Request](args)
-  let localIp = getPrimaryIPAddr(req.dstIp)
-  try:
-    let connectFuture = newFuture[AsyncSocket]("respond")
-    let portRange = predictPortRange(req.dstPorts)
-    for dstPort in portRange:
-      asyncCheck connect(localIp, req.srcPorts[0], req.dstIp, req.dstPorts[0],
-                         connectFuture)
-    await connectFuture or sleepAsync(Timeout)
-    if connectFuture.finished():
-      result = connectFuture.read()
-    else:
-      raise newException(PunchHoleError, "timeout")
-  except OSError as e:
-    raise newException(PunchHoleError, e.msg)
diff --git a/tcp_syni.nim b/tcp_syni.nim
new file mode 100644
index 0000000..c278f81
--- /dev/null
+++ b/tcp_syni.nim
@@ -0,0 +1,190 @@
+from nativesockets import Protocol, setSockOptInt
+from net import IpAddress, Port, `$`, `==`
+from random import randomize, rand
+from strutils import join
+import asyncdispatch, asyncnet, strformat
+import ip_packet
+import message
+import network_interface
+import options
+import port_prediction
+import puncher
+import raw_socket
+import utils
+
+export puncher
+
+type
+  TcpSyniPuncher* = ref object of Puncher
+
+  InitiateRequest = object
+    srcIp: IpAddress
+    srcPorts: seq[Port]
+    dstIp: IpAddress
+    dstPorts: seq[Port]
+
+  RespondRequest = object
+    dstIp: IpAddress
+    dstPorts: seq[Port]
+    srcIp: IpAddress
+    srcPorts: seq[Port]
+    seqNums: seq[uint32]
+
+  TcpSyniInitiateAttempt = ref object of Attempt
+
+  TcpSyniRespondAttempt = ref object of Attempt
+    seqNums: seq[uint32]
+
+var IPPROTO_IP {.importc: "IPPROTO_IP", header: "<netinet/in.h>".}: cint
+var IP_TTL {.importc: "IP_TTL", header: "<netinet/in.h>".}: cint
+
+proc captureSeqNumbers(attempt: Attempt, cb: PunchProgressCb) {.async.} =
+  # FIXME: timeout?
+  let iface = getNetworkInterface(attempt.srcIp)
+  let captureFd = setupEthernetCapturingSocket(iface)
+  var seqNums = newSeq[uint32]()
+  while seqNums.len < attempt.dstPorts.len:
+    let packet = await captureFd.recv(4000)
+    if packet == "":
+      break
+    let parsed = parseEthernetPacket(packet)
+    if parsed.protocol == tcp and
+       parsed.ipAddrSrc == attempt.srcIp and
+       parsed.tcpPortSrc.int == attempt.srcPort.int and
+       parsed.ipAddrDst == attempt.dstIp and
+       parsed.tcpFlags == {SYN}:
+      for port in attempt.dstPorts:
+        if parsed.tcpPortDst.int == port.int:
+          seqNums.add(parsed.tcpSeqNumber)
+          break
+  closeSocket(captureFd)
+  await cb(seqNums.join(","))
+
+proc captureAndResendAck(attempt: Attempt) {.async.} =
+  let iface = getNetworkInterface(attempt.srcIp)
+  let captureFd = setupEthernetCapturingSocket(iface)
+  let injectFd = setupTcpInjectingSocket()
+  block loops:
+    while true:
+      let packet = await captureFd.recv(4000)
+      if packet == "":
+        break
+      var parsed = parseEthernetPacket(packet)
+      if parsed.protocol == tcp and
+         parsed.ipAddrSrc == attempt.srcIp and
+         parsed.tcpPortSrc.int == attempt.srcPort.int and
+         parsed.ipAddrDst == attempt.dstIp and
+         parsed.tcpFlags == {ACK}:
+        for port in attempt.dstPorts:
+          if parsed.tcpPortDst.int == port.int:
+            parsed.ipTTL = 64
+            echo &"[{parsed.ipAddrSrc}:{parsed.tcpPortSrc.int} -> {parsed.ipAddrDst}:{parsed.tcpPortDst}, SEQ {parsed.tcpSeqNumber}] resending ACK with TTL {parsed.ipTTL}"
+            await injectFd.injectTcpPacket(parsed)
+            break loops
+  closeSocket(captureFd)
+  closeSocket(injectFd)
+
+proc connect(srcIp: IpAddress, srcPort: Port, dstIp: IpAddress, dstPort: Port,
+               future: Future[AsyncSocket]) {.async.} =
+  let sock = newAsyncSocket()
+  sock.setSockOpt(OptReuseAddr, true)
+  sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 2)
+  echo &"connect {srcIp}:{srcPort} -> {dstIp}:{dstPort}"
+  sock.bindAddr(srcPort, $srcIp)
+  try:
+    await sock.connect($dstIp, dstPort)
+    sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 64)
+    future.complete(sock)
+  except OSError as e:
+    echo &"connection {srcIP}:{srcPort.int} -> {dstIp}:{dstPort.int} failed: ", e.msg
+    sock.close()
+
+proc injectSynPackets(attempt: TcpSyniRespondAttempt) {.async.} =
+  let injectFd = setupTcpInjectingSocket()
+  for dstPort in attempt.dstPorts:
+    let synOut = IpPacket(protocol: tcp, ipAddrSrc: attempt.srcIp,
+                          ipAddrDst: attempt.dstIp, ipTTL: 2,
+                          tcpPortSrc: attempt.srcPort, tcpPortDst: dstPort,
+                          tcpSeqNumber: rand(uint32), tcpAckNumber: 0,
+                          tcpFlags: {SYN}, tcpWindowSize: 1452 * 10)
+    echo &"[{synOut.ipAddrSrc}:{synOut.tcpPortSrc} -> {synOut.ipAddrDst}:{synOut.tcpPortDst}, SEQ {synOut.tcpSeqNumber}] injecting outgoing SYN"
+    await injectFd.injectTcpPacket(synOut)
+    for seqNum in attempt.seqNums:
+      let synIn = IpPacket(protocol: tcp, ipAddrSrc: attempt.dstIp,
+                           ipAddrDst: attempt.srcIp, ipTTL: 64,
+                           tcpPortSrc: dstPort,
+                           tcpPortDst: attempt.srcPort,
+                           tcpSeqNumber: seqNum, tcpAckNumber: 0,
+                           tcpFlags: {SYN}, tcpWindowSize: 1452 * 10)
+      echo &"[{synIn.ipAddrSrc}:{synIn.tcpPortSrc} -> {synIn.ipAddrDst}:{synIn.tcpPortDst}, SEQ {synIn.tcpSeqNumber}] injecting incoming SYN"
+      await injectFd.injectTcpPacket(synIn)
+  closeSocket(injectFd)
+
+proc initTcpSyniPuncher*(): TcpSyniPuncher =
+  randomize()
+  TcpSyniPuncher()
+
+method cleanup*(attempt: TcpSyniInitiateAttempt) {.async.} =
+  await deleteFirewallRules(attempt)
+
+method cleanup*(attempt: TcpSyniRespondAttempt) {.async.} =
+  await deleteFirewallRules(attempt)
+
+method getProtocol*(puncher: TcpSyniPuncher): Protocol =
+  IPPROTO_TCP
+
+method parseInitiateRequest*(puncher: TcpSyniPuncher, args: string): Attempt =
+  let parsed = parseMessage[InitiateRequest](args)
+  let localIp = getPrimaryIPAddr(parsed.dstIp)
+  let predictedDstPorts = predictPortRange(parsed.dstPorts)
+  TcpSyniInitiateAttempt(srcIp: localIp, srcPort: parsed.srcPorts[0],
+                         dstIp: parsed.dstIp, dstPorts: predictedDstPorts,
+                         acceptFuture: none(Future[AsyncSocket]))
+
+method parseRespondRequest*(puncher: TcpSyniPuncher, args: string): Attempt =
+  let parsed = parseMessage[RespondRequest](args)
+  let localIp = getPrimaryIPAddr(parsed.dstIp)
+  let predictedDstPorts = predictPortRange(parsed.dstPorts)
+  let acceptFuture = newFuture[AsyncSocket]("parseRespondRequest")
+  TcpSyniRespondAttempt(srcIp: localIp, srcPort: parsed.srcPorts[0],
+                        dstIp: parsed.dstIp, dstPorts: predictedDstPorts,
+                        acceptFuture: some(acceptFuture),
+                        seqNums: parsed.seqNums)
+
+method initiate*(puncher: TcpSyniPuncher, attempt: Attempt,
+                 progress: PunchProgressCb): Future[AsyncSocket] {.async.} =
+  assert(attempt of TcpSyniInitiateAttempt, "unexpected attempt type")
+  assert(attempt.acceptFuture.isNone(), "expected attempt without acceptFuture")
+  await addFirewallRules(attempt)
+  asyncCheck captureSeqNumbers(attempt, progress)
+  asyncCheck captureAndResendAck(attempt)
+  try:
+    let connectFuture = newFuture[AsyncSocket]("connect")
+    for dstPort in attempt.dstPorts:
+      asyncCheck connect(attempt.srcIp, attempt.srcPort, attempt.dstIp,
+                         dstPort, connectFuture)
+    await connectFuture or sleepAsync(Timeout)
+    await deleteFirewallRules(attempt)
+    if connectFuture.finished():
+      result = connectFuture.read()
+    else:
+      raise newException(PunchHoleError, "timeout")
+  except OSError as e:
+    raise newException(PunchHoleError, e.msg)
+
+method respond*(puncher: TcpSyniPuncher, attempt: Attempt):
+               Future[AsyncSocket] {.async.} =
+  assert(attempt of TcpSyniRespondAttempt, "unexpected attempt type")
+  assert(attempt.acceptFuture.isSome(), "expected attempt with acceptFuture")
+  try:
+    let acceptFuture = attempt.acceptFuture.get()
+    await addFirewallRules(attempt) # FIXME: needed?
+    await injectSynPackets(TcpSyniRespondAttempt(attempt))
+    await acceptFuture or sleepAsync(Timeout)
+    await deleteFirewallRules(attempt) # FIXME: needed?
+    if acceptFuture.finished():
+      result = acceptFuture.read()
+    else:
+      raise newException(PunchHoleError, "timeout")
+  except OSError as e:
+    raise newException(PunchHoleError, e.msg)
diff --git a/tcp_syni_initiator.nim b/tcp_syni_initiator.nim
deleted file mode 100644
index d44e334..0000000
--- a/tcp_syni_initiator.nim
+++ /dev/null
@@ -1,120 +0,0 @@
-import asyncdispatch, asyncnet, strformat
-from net import IpAddress, Port, `$`, `==`
-from nativesockets import setSockOptInt
-from strutils import join
-import ip_packet
-import message
-import network_interface
-import port_prediction
-import puncher
-import raw_socket
-import utils
-
-export Puncher, Initiator, PunchProgressCb, PunchHoleError, cleanup, initiate
-
-type
-  TcpSyniInitiator* = ref object of Initiator
-
-  Request = object
-    srcIp: IpAddress
-    srcPorts: seq[Port]
-    dstIp: IpAddress
-    dstPorts: seq[Port]
-
-var IPPROTO_IP {.importc: "IPPROTO_IP", header: "<netinet/in.h>".}: cint
-var IP_TTL {.importc: "IP_TTL", header: "<netinet/in.h>".}: cint
-
-method cleanup*(puncher: TcpSyniInitiator): Future[void] {.async.} =
-  while puncher.attempts.len() != 0:
-    await puncher.attempts.pop().deleteFirewallRules()
-
-proc initTcpSyniInitiator*(): TcpSyniInitiator =
-  TcpSyniInitiator()
-
-proc captureSeqNumbers(attempt: Attempt, cb: PunchProgressCb) {.async.} =
-  # FIXME: timeout?
-  let iface = getNetworkInterface(attempt.srcIp)
-  let captureFd = setupEthernetCapturingSocket(iface)
-  var seqNums = newSeq[uint32]()
-  while seqNums.len < attempt.dstPorts.len:
-    let packet = await captureFd.recv(4000)
-    if packet == "":
-      break
-    let parsed = parseEthernetPacket(packet)
-    if parsed.protocol == tcp and
-       parsed.ipAddrSrc == attempt.srcIp and
-       parsed.tcpPortSrc.int == attempt.srcPort.int and
-       parsed.ipAddrDst == attempt.dstIp and
-       parsed.tcpFlags == {SYN}:
-      for port in attempt.dstPorts:
-        if parsed.tcpPortDst.int == port.int:
-          seqNums.add(parsed.tcpSeqNumber)
-          break
-  closeSocket(captureFd)
-  await cb(seqNums.join(","))
-
-proc captureAndResendAck(attempt: Attempt) {.async.} =
-  let iface = getNetworkInterface(attempt.srcIp)
-  let captureFd = setupEthernetCapturingSocket(iface)
-  let injectFd = setupTcpInjectingSocket()
-  block loops:
-    while true:
-      let packet = await captureFd.recv(4000)
-      if packet == "":
-        break
-      var parsed = parseEthernetPacket(packet)
-      if parsed.protocol == tcp and
-         parsed.ipAddrSrc == attempt.srcIp and
-         parsed.tcpPortSrc.int == attempt.srcPort.int and
-         parsed.ipAddrDst == attempt.dstIp and
-         parsed.tcpFlags == {ACK}:
-        for port in attempt.dstPorts:
-          if parsed.tcpPortDst.int == port.int:
-            parsed.ipTTL = 64
-            echo &"[{parsed.ipAddrSrc}:{parsed.tcpPortSrc.int} -> {parsed.ipAddrDst}:{parsed.tcpPortDst}, SEQ {parsed.tcpSeqNumber}] resending ACK with TTL {parsed.ipTTL}"
-            await injectFd.injectTcpPacket(parsed)
-            break loops
-  closeSocket(captureFd)
-  closeSocket(injectFd)
-
-proc connect(srcIp: IpAddress, srcPort: Port, dstIp: IpAddress, dstPort: Port,
-               future: Future[AsyncSocket]) {.async.} =
-  let sock = newAsyncSocket()
-  sock.setSockOpt(OptReuseAddr, true)
-  sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 2)
-  echo &"connect {srcIp}:{srcPort} -> {dstIp}:{dstPort}"
-  sock.bindAddr(srcPort, $srcIp)
-  try:
-    await sock.connect($dstIp, dstPort)
-    sock.getFd.setSockOptInt(IPPROTO_IP, IP_TTL, 64)
-    future.complete(sock)
-  except OSError as e:
-    echo &"connection {srcIP}:{srcPort.int} -> {dstIp}:{dstPort.int} failed: ", e.msg
-    sock.close()
-
-method initiate*(puncher: TcpSyniInitiator, args: string,
-                 progressCb: PunchProgressCb): Future[AsyncSocket] {.async.} =
-  let req = parseMessage[Request](args)
-  let localIp = getPrimaryIPAddr(req.dstIp)
-  if puncher.findAttempt(localIp, req.srcPorts[0], req.dstIp, req.dstPorts) != -1:
-    raise newException(PunchHoleError, "hole punching for given parameters already active")
-  let attempt = Attempt(srcIp: localIp, srcPort: req.srcPorts[0], dstIp: req.dstIp,
-                        dstPorts: predictPortRange(req.dstPorts))
-  puncher.attempts.add(attempt)
-  await attempt.addFirewallRules()
-  asyncCheck attempt.captureSeqNumbers(progressCb)
-  asyncCheck attempt.captureAndResendAck()
-  try:
-    let connectFuture = newFuture[AsyncSocket]("connect")
-    for dstPort in attempt.dstPorts:
-      asyncCheck connect(attempt.srcIp, attempt.srcPort, attempt.dstIp,
-                         dstPort, connectFuture)
-    await connectFuture or sleepAsync(Timeout)
-    await attempt.deleteFirewallRules()
-    puncher.attempts.del(puncher.attempts.find(attempt))
-    if connectFuture.finished():
-      result = connectFuture.read()
-    else:
-      raise newException(PunchHoleError, "timeout")
-  except OSError as e:
-    raise newException(PunchHoleError, e.msg)
diff --git a/tcp_syni_responder.nim b/tcp_syni_responder.nim
deleted file mode 100644
index 37facfa..0000000
--- a/tcp_syni_responder.nim
+++ /dev/null
@@ -1,114 +0,0 @@
-import asyncdispatch, asyncnet, strformat
-from net import IpAddress, Port, `$`, `==`, parseIpAddress
-from random import randomize, rand
-from sequtils import any
-import ip_packet
-import message
-import port_prediction
-import puncher
-import raw_socket
-import utils
-
-export Puncher, Responder, PunchHoleError, cleanup, respond
-
-type
-  TSRAttempt = ref object of Attempt
-    seqNums: seq[uint32]
-    future: Future[AsyncSocket]
-
-  TcpSyniResponder* = ref object of Responder
-
-  Request = object
-    dstIp: IpAddress
-    dstPorts: seq[Port]
-    srcIp: IpAddress
-    srcPorts: seq[Port]
-    seqNums: seq[uint32]
-
-method cleanup*(puncher: TcpSyniResponder) {.async.} =
-  while puncher.attempts.len() != 0:
-    await puncher.attempts.pop().deleteFirewallRules()
-
-proc initTcpSyniResponder*(): TcpSyniResponder =
-  randomize()
-  TcpSyniResponder()
-
-proc injectSynPackets(attempt: TSRAttempt) {.async.} =
-  let injectFd = setupTcpInjectingSocket()
-  for dstPort in attempt.dstPorts:
-    let synOut = IpPacket(protocol: tcp, ipAddrSrc: attempt.srcIp,
-                          ipAddrDst: attempt.dstIp, ipTTL: 2,
-                          tcpPortSrc: attempt.srcPort, tcpPortDst: dstPort,
-                          tcpSeqNumber: rand(uint32), tcpAckNumber: 0,
-                          tcpFlags: {SYN}, tcpWindowSize: 1452 * 10)
-    echo &"[{synOut.ipAddrSrc}:{synOut.tcpPortSrc} -> {synOut.ipAddrDst}:{synOut.tcpPortDst}, SEQ {synOut.tcpSeqNumber}] injecting outgoing SYN"
-    await injectFd.injectTcpPacket(synOut)
-    for seqNum in attempt.seqNums:
-      let synIn = IpPacket(protocol: tcp, ipAddrSrc: attempt.dstIp,
-                           ipAddrDst: attempt.srcIp, ipTTL: 64,
-                           tcpPortSrc: dstPort,
-                           tcpPortDst: attempt.srcPort,
-                           tcpSeqNumber: seqNum, tcpAckNumber: 0,
-                           tcpFlags: {SYN}, tcpWindowSize: 1452 * 10)
-      echo &"[{synIn.ipAddrSrc}:{synIn.tcpPortSrc} -> {synIn.ipAddrDst}:{synIn.tcpPortDst}, SEQ {synIn.tcpSeqNumber}] injecting incoming SYN"
-      await injectFd.injectTcpPacket(synIn)
-  closeSocket(injectFd)
-
-proc accept(puncher: TcpSyniResponder, srcIp: IpAddress,
-            srcPort: Port) {.async.} =
-  let sock = newAsyncSocket()
-  sock.setSockOpt(OptReuseAddr, true)
-  sock.bindAddr(srcPort, $srcIp)
-  sock.listen()
-  while true:
-    let acceptFuture = sock.accept()
-    await acceptFuture or sleepAsync(Timeout)
-    if acceptFuture.finished():
-      let peer = acceptFuture.read()
-      let (peerAddr, peerPort) = peer.getPeerAddr()
-      let peerIp = parseIpAddress(peerAddr)
-      let i = puncher.findAttempt(srcIp, srcPort, peerIp, @[peerPort])
-      if i == -1:
-        echo "Accepted connection, but no attempt found. Discarding."
-        peer.close()
-        continue
-      else:
-        let attempt = TSRAttempt(puncher.attempts[i])
-        attempt.future.complete(peer)
-    let attempts = puncher.findAttemptsByLocalAddr(srcIp, srcPort)
-    # FIXME: should attempts have timestamps, so we can decide here which ones to delete?
-    if attempts.len() <= 1:
-      break
-  sock.close()
-
-method respond*(puncher: TcpSyniResponder, args: string):
-               Future[AsyncSocket] {.async.} =
-  let req = parseMessage[Request](args)
-  let localIp = getPrimaryIPAddr(req.dstIp)
-  let existingAttempts = puncher.findAttemptsByLocalAddr(localIp, req.srcPorts[0])
-  if existingAttempts.len() == 0:
-    echo &"accepting connections from {req.dstIp}:{req.dstPorts[0].int}"
-    asyncCheck puncher.accept(localIp, req.srcPorts[0])
-  else:
-    for a in existingAttempts:
-      if a.dstIp == req.dstIp and
-         a.dstPorts.any(proc (p: Port): bool = p in req.dstPorts):
-        raise newException(PunchHoleError, "hole punching for given parameters already active")
-  try:
-    let attempt = TSRAttempt(srcIp: localIp, srcPort: req.srcPorts[0],
-                             dstIp: req.dstIp,
-                             dstPorts: predictPortRange(req.dstPorts),
-                             seqNums: req.seqNums,
-                             future: newFuture[AsyncSocket]("respond"))
-    puncher.attempts.add(attempt)
-    await attempt.addFirewallRules() # FIXME: needed?
-    await attempt.injectSynPackets()
-    await attempt.future or sleepAsync(Timeout)
-    await attempt.deleteFirewallRules() # FIXME: needed?
-    puncher.attempts.del(puncher.attempts.find(attempt))
-    if attempt.future.finished():
-      result = attempt.future.read()
-    else:
-      raise newException(PunchHoleError, "timeout")
-  except OSError as e:
-    raise newException(PunchHoleError, e.msg)