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5764 :: Problem of running http port forwarding

• geohuz (orginal) [2020-01-02T12:14:45+01:00] view original

  I recently trying to follow the Nim days 15: https://xmonader.github.io/nimdays/day15_tcprouter.html, but when I tried to set up the server to serve on port say 11000 and forward to my local hosted http server 6543, I just got all these kind of errors:

  
  Async traceback:
    /Users/geohuz/Coding/nimlearn/portForwarding2.nim(69)                          portForwarding2
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncdispatch.nim(1874) runForever
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncdispatch.nim(1569) poll
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncdispatch.nim(1335) runOnce
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncdispatch.nim(210)  processPendingCallbacks
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncmacro.nim(34)      remoteHasDataNimAsyncContinue
    /Users/geohuz/Coding/nimlearn/portForwarding2.nim(37)                          remoteHasDataIter
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncmacro.nim(313)     send
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncmacro.nim(34)      sendNimAsyncContinue
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncnet.nim(446)       sendIter
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/pure/asyncdispatch.nim(1843) send
    /Users/geohuz/.choosenim/toolchains/nim-1.0.4/lib/system/fatal.nim(39)         sysFatal
  Exception message: index out of bounds, the container is empty
  Exception type:
   in remote has data loop
  got data:
  index out of bounds, the container is empty
  Run

  and here is the code:

  
  import  strformat, tables, json, strutils, sequtils, hashes, net, asyncdispatch, asyncnet, os, strutils, parseutils, deques, options, net
  
  type ForwardOptions = object
    listenAddr*: string
    listenPort*: Port
    toAddr*: string
    toPort*: Port
  
  type Forwarder = object of RootObj
    options*: ForwardOptions
  
  proc processClient(this: ref Forwarder, client: AsyncSocket) {.async.} =
    let remote = newAsyncSocket(buffered=false)
    await remote.connect(this.options.toAddr, this.options.toPort)
    
    proc clientHasData() {.async.} =
      while not client.isClosed and not remote.isClosed:
        echo "in client has data loop"
        let data = await client.recv(1024)
        echo "got data: " & data
        try:
          await remote.send(data)
        except:
          echo getCurrentExceptionMsg()
      client.close()
      remote.close()
    
    proc remoteHasData() {.async.} =
      while not remote.isClosed and not client.isClosed:
        echo " in remote has data loop"
        let data = await remote.recv(1024)
        echo "got data: " & data
        try:
          await client.send(data)
        except:
          echo getCurrentExceptionMsg()
      client.close()
      remote.close()
    
    try:
      asyncCheck clientHasData()
      asyncCheck remoteHasData()
    except:
      echo getCurrentExceptionMsg()
  
  proc serve(this: ref Forwarder) {.async.} =
    var server = newAsyncSocket(buffered=false)
    server.setSockOpt(OptReuseAddr, true)
    server.bindAddr(this.options.listenPort, this.options.listenAddr)
    echo fmt"Started tcp server... {this.options.listenAddr}:{this.options.listenPort} "
    server.listen()
    
    while true:
      let client = await server.accept()
      echo "..Got connection "
      
      asyncCheck this.processClient(client)
  
  proc newForwarder(opts: ForwardOptions): ref Forwarder =
    result = new(Forwarder)
    result.options = opts
  
  let opts = ForwardOptions(listenAddr:"127.0.0.1", listenPort:11000.Port, toAddr:"127.0.0.1", toPort:6543.Port)
  var f = newForwarder(opts)
  asyncCheck f.serve()
  runForever()
  Run

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• hasan (orginal) [2020-01-05T19:02:47+01:00] view original

  Does it work if you remove the try/except blocks you added in ...HasData procedures? If it does, then the issue is as roughly explained here: https://nim-lang.org/docs/asyncdispatch.html#asynchronous-procedures-handling-exceptions

  It seems like async and exceptions don't go very well together, at least not yet.

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• geohuz (orginal) [2020-01-06T09:51:37+01:00] view original

  So I changed code as below:

  
  proc processClient(this: ref Forwarder, client: AsyncSocket) {.async.} =
    let remote = newAsyncSocket(buffered=false)
    await remote.connect(this.options.toAddr, this.options.toPort)
    
    proc clientHasData() {.async.} =
      while not client.isClosed and not remote.isClosed:
        let recv = client.recv(1024)
        yield recv
        if recv.failed:
          echo "recv error........."
        else:
          let send = remote.send(recv.read)
          yield send
          if send.failed:
            echo "send error...."
      client.close()
      remote.close()
    
    proc remoteHasData() {.async.} =
      while not remote.isClosed and not client.isClosed:
        let recv = remote.recv(1024)
        yield recv
        if recv.failed:
          echo "recv error...."
        else:
          let send = client.send(recv.read)
          yield send
          if send.failed:
            echo "send error...."
      client.close()
      remote.close()
    
    try:
      asyncCheck clientHasData()
      asyncCheck remoteHasData()
    except:
      echo getCurrentExceptionMsg()
  Run

  but I still got numerous "send error...", but the forwarding seems working.

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