UDP broadcast and automatic server discovery in python, TCP socket unavailable -

-

i'm developing reverse shell application in python, , right i'm trying implement autodiscovery feature. should work follows:

  1. the server broadcasts ip/port listens connections on, , waits client. if no client tries connect in few seconds, broadcasts again (and repeat till connection).
  2. the client tries receive broadcast of server, , connects advertised ip/port.

the broadcast works fine, client receives ip/port , connects, after using connected pair of ports (server side):

socket.error: [errno 35] resource temporarily unavailable

server side test code:

sckt = socket.socket(socket.af_inet, socket.sock_stream) sckt.setsockopt(socket.sol_socket, socket.so_reuseaddr, 1) sckt.settimeout(2) sckt.bind(('', 9999)) sckt.listen(5)  broadcastsocket = socket.socket(socket.af_inet, socket.sock_dgram) broadcastsocket.setsockopt(socket.sol_socket, socket.so_broadcast, 1) broadcastsocket.setsockopt(socket.sol_socket, socket.so_reuseaddr, 1) while true:     broadcastsocket.sendto(socket.gethostbyname(socket.getfqdn()) + ' ' + str(9999), ('<broadcast>', 8888))     try:         sock, address = sckt.accept()         break     except socket.timeout:         pass broadcastsocket.close() sckt.settimeout(none)  sock.send('test') # if add time.sleep(1) here, works, don't why # sock unavailable @ first, available second later print sock.recv(1) # fails # note fails recv buffer size, instance 1024

why on earth want receive 1 byte of data, might ask. have algorithm prefixes messages lengths, , receiver reads prefix byte-by-byte till delimiter, thats why. client side test code:

broadcastsocket = socket.socket(socket.af_inet, socket.sock_dgram) broadcastsocket.setsockopt(socket.sol_socket, socket.so_reuseaddr, 1) broadcastsocket.settimeout(3) broadcastsocket.bind(('', 8888)) while true:     try:         data = broadcastsocket.recv(1024)         break     except socket.timeout:         pass broadcastsocket.close()  sckt = socket.socket(socket.af_inet, socket.sock_stream) sckt.setsockopt(socket.sol_socket, socket.so_reuseaddr, 1) sckt.connect((str(data.split()[0]), int(data.split()[1])))  print sckt.recv(1024) sckt.send('lel')

if omit whole broadcast , autodiscovery part of code , manually enter ip/port of server print sock.recv(1) doesn't fail. clues on issue might be?

change sckt.settimeout(none) sock.settimout(none) in server code.

you want have accepted socket in blocking mode , not accepting one.

this ensures sckt.recv waits incoming message client.

p.s. sock.setblocking(1) same


Comments

Post a Comment

Popular posts from this blog

c++ - llvm function pass ReplaceInstWithInst malloc -

-
#include "llvm/pass.h" #include "llvm/ir/module.h" #include "llvm/ir/function.h" #include "llvm/support/raw_ostream.h" #include "llvm/ir/legacypassmanager.h" #include "llvm/ir/instrtypes.h" #include "llvm/transforms/ipo/passmanagerbuilder.h" #include "llvm/ir/irbuilder.h" #include "llvm/transforms/utils/basicblockutils.h" using namespace llvm; namespace { struct replacepass : public functionpass { static char id; replacepass() : functionpass(id) {} virtual bool runonfunction(function &f) { allocainst* insttoreplace = ??? basicblock::iterator ii(insttoreplace); replaceinstwithinst(insttoreplace->getparent()->getinstlist(), ii, new allocainst(type::int32ty, 0, insttoreplace)); return true; } }; } char replacepass::id = 0; static void registerreplacepass(const passmanagerbuilder &, legacy::passmanagerbase &pm) { pm.add(new re
Read more

java.lang.NoClassDefFoundError When Creating New Android Project -

-
i've tried installing (and re-installing) android studio several times now, , each time, studio isn't able create new android project. when attempt initial android studio window (ie. basic 'create', 'open', 'import' etc options), i'm asked of questions in wizard, brief progress dialog, followed nothing @ all. if open incomplete project process creates choosing 'open' list, can try choosing create new android project menu. this has same issue, error message in output console time... java.lang.noclassdeffounderror: com/sun/xml/internal/bind/v2/model/annotation/annotationreader (wrong name: com/sun/xml/internal/bind/v0/model/qnnotation/annotationreader) note: when installed android studio, installed incompatible jdk (1.8, not 1.7). have had go default project settings change jdk uses 1.8. does know how can avoid this? there place should downloading jxb classes? missing in java paths? this appears have been caused cor
Read more

Decoding a Python 2 `tempfile` with python-future -

-
i'm attempting write python 2/3 compatible routine fetch csv file, decode latin_1 unicode , feed csv.dictreader in robust, scalable manner. for python 2/3 support, i'm using python-future including imporing open builtins , , importing unicode_literals consistent behaviour i'm hoping handle exceptionally large files spilling disk, using tempfile.spooledtemporaryfile i'm using io.textiowrapper handle decoding latin_1 encoding before feeding dictreader this works fine under python 3. the problem textiowrapper expects wrap stream conforms bufferediobase . unfortunately under python 2, although have imported python 3-style open , vanilla python 2 tempfile.spooledtemporaryfile still of course returns python 2 cstringio.stringo , instead of python 3 io.bytesio required textiowrapper . i can think of these possible approaches: wrap python 2 cstringio.stringo python 3-style io.bytesio . i'm not sure how approach - need write such wrapper or 1 ex
Read more