diff --git a/.travis.yml b/.travis.yml
index 0934039..d83083a 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,7 @@
 language: python
 python:
   - "2.7"
+  - "3.3"
 
 install:
   - pip install .
diff --git a/amodem/calib.py b/amodem/calib.py
index 53446b7..06197f7 100755
--- a/amodem/calib.py
+++ b/amodem/calib.py
@@ -1,9 +1,10 @@
 #!/usr/bin/env python
 import numpy as np
-import common
-import config
-import sigproc
-import wave
+
+from . import common
+from . import config
+from . import sigproc
+from . import wave
 
 Tsample = 1
 t = np.arange(int(Tsample * config.Fs)) * config.Ts
@@ -22,6 +23,7 @@ def send():
     except KeyboardInterrupt:
         p.kill()
 
+
 def recv():
     p = wave.record('-', stdout=wave.sp.PIPE)
     try:
@@ -36,13 +38,15 @@ def recv():
                 continue
             x = x - np.mean(x)
 
-            c = np.abs(np.dot(x, sig)) / (np.sqrt(0.5 * len(x)) * sigproc.norm(x))
+            normalization_factor = np.sqrt(0.5 * len(x)) * sigproc.norm(x)
+            coherence = np.abs(np.dot(x, sig)) / normalization_factor
             z = np.dot(x, sig.conj()) / (0.5 * len(x))
-            amp = np.abs(z)
+            amplitude = np.abs(z)
             phase = np.angle(z)
             peak = np.max(np.abs(x))
-            print('coherence={:.3f} amp={:.3f} phase={:.1f} peak={:.3f}'.format(
-                  c, amp, phase * 180 / np.pi, peak))
+
+            fmt = 'coherence={:.3f} amplitude={:.3f} phase={:+.1f} peak={:.3f}'
+            print(fmt.format(coherence, amplitude, phase * 180 / np.pi, peak))
     except KeyboardInterrupt:
         p.kill()
 
diff --git a/amodem/common.py b/amodem/common.py
index da9344c..cf9e078 100644
--- a/amodem/common.py
+++ b/amodem/common.py
@@ -41,7 +41,7 @@ def load(fileobj):
 
 
 def loads(data):
-    x = np.fromstring(data, dtype='int16')
+    x = np.frombuffer(data, dtype='int16')
     x = x / scaling
     return x
 
@@ -83,7 +83,7 @@ class Splitter(object):
         while True:
             if all(self.read):
                 try:
-                    self.last = self.iterable.next()
+                    self.last = next(self.iterable)
                 except StopIteration:
                     return
 
@@ -108,3 +108,9 @@ def icapture(iterable, result):
 
 def take(iterable, n):
     return np.array(list(itertools.islice(iterable, n)))
+
+
+try:
+    izip = itertools.izip
+except AttributeError:
+    izip = zip  # Python 3
diff --git a/amodem/ecc.py b/amodem/ecc.py
index 1da4f32..f69445c 100644
--- a/amodem/ecc.py
+++ b/amodem/ecc.py
@@ -1,7 +1,7 @@
 ''' Reed-Solomon CODEC. '''
 from reedsolo import rs_encode_msg, rs_correct_msg
 
-import common
+from . import common
 
 import logging
 log = logging.getLogger(__name__)
@@ -17,7 +17,8 @@ def end_of_stream(size):
 def encode(data, nsym=DEFAULT_NSYM):
     chunk_size = BLOCK_SIZE - nsym - 1
 
-    for _, chunk in common.iterate(data, chunk_size, bytearray, truncate=False):
+    for _, chunk in common.iterate(data=data, size=chunk_size,
+                                   func=bytearray, truncate=False):
         size = len(chunk)
         if size < chunk_size:
             padding = [0] * (chunk_size - size)
diff --git a/amodem/loop.py b/amodem/loop.py
index a1a409e..beef6cb 100644
--- a/amodem/loop.py
+++ b/amodem/loop.py
@@ -1,8 +1,9 @@
 import numpy as np
 import itertools
 
-import sampling
-import sigproc
+from . import sampling
+from . import sigproc
+from . import common
 
 
 class Filter(object):
@@ -33,4 +34,4 @@ class FreqLoop(object):
             self.gens.append(gen)
 
     def __iter__(self):
-        return itertools.izip(*self.gens)
+        return common.izip(*self.gens)
diff --git a/amodem/recv.py b/amodem/recv.py
index 08866fa..d47fcba 100755
--- a/amodem/recv.py
+++ b/amodem/recv.py
@@ -8,21 +8,24 @@ import time
 import sys
 import os
 
+import bitarray
+
 log = logging.getLogger(__name__)
 
-import stream
-import sigproc
-import loop
-import train
-import common
-import config
+from . import stream
+from . import sigproc
+from . import loop
+from . import train
+from . import common
+from . import config
+from . import ecc
 
 modem = sigproc.MODEM(config)
 
 
 if os.environ.get('PYLAB') == '1':
-    import pylab
-    import show
+    from . import pylab
+    from . import show
     WIDTH = np.floor(np.sqrt(len(modem.freqs)))
     HEIGHT = np.ceil(len(modem.freqs) / float(WIDTH))
 else:
@@ -190,7 +193,7 @@ def demodulate(symbols, filters, freqs, sampler):
     stats['rx_start'] = time.time()
 
     log.info('Demodulation started')
-    for i, block in enumerate(itertools.izip(*streams)):  # block per frequency
+    for i, block in enumerate(common.izip(*streams)):  # block per frequency
         for bits in block:
             stats['rx_bits'] = stats['rx_bits'] + len(bits)
             yield bits
@@ -223,9 +226,6 @@ def receive(signal, freqs, gain=1.0):
 
 
 def decode(bits_iterator):
-    import bitarray
-    import ecc
-
     def blocks():
         while True:
             bits = itertools.islice(bits_iterator, 8 * ecc.BLOCK_SIZE)
@@ -238,11 +238,16 @@ def decode(bits_iterator):
     return ecc.decode(blocks())
 
 
+def iread(fd):
+    reader = stream.Reader(fd, data_type=common.loads)
+    return itertools.chain.from_iterable(reader)
+
+
 def main(args):
 
     log.info('Running MODEM @ {:.1f} kbps'.format(modem.modem_bps / 1e3))
 
-    signal = stream.iread(args.input)
+    signal = iread(args.input)
     skipped = common.take(signal, args.skip)
     log.debug('Skipping first %.3f seconds', len(skipped) / float(modem.baud))
 
@@ -282,8 +287,10 @@ if __name__ == '__main__':
     p = argparse.ArgumentParser()
     p.add_argument('--skip', type=int, default=100,
                    help='skip initial N samples, due to spurious spikes')
-    p.add_argument('-i', '--input', type=argparse.FileType('r'), default=sys.stdin)
-    p.add_argument('-o', '--output', type=argparse.FileType('w'), default=sys.stdout)
+    p.add_argument('-i', '--input', type=argparse.FileType('rb'),
+                   default=sys.stdin)
+    p.add_argument('-o', '--output', type=argparse.FileType('wb'),
+                   default=sys.stdout)
     args = p.parse_args()
     try:
         main(args)
diff --git a/amodem/sampling.py b/amodem/sampling.py
index 56a68d3..e55221d 100755
--- a/amodem/sampling.py
+++ b/amodem/sampling.py
@@ -49,6 +49,8 @@ class Sampler(object):
     def next(self):
         return self._sample() * self.gain
 
+    __next__ = next
+
     def _sample(self):
         offset = self.offset
         # offset = k + (j / self.resolution)
@@ -58,7 +60,7 @@ class Sampler(object):
         end = k + self.width
         while self.index < end:
             self.buff[:-1] = self.buff[1:]
-            self.buff[-1] = self.src.next()  # throws StopIteration
+            self.buff[-1] = next(self.src)  # throws StopIteration
             self.index += 1
 
         self.offset += self.freq
diff --git a/amodem/send.py b/amodem/send.py
index 6322224..fe9e7bf 100755
--- a/amodem/send.py
+++ b/amodem/send.py
@@ -7,19 +7,22 @@ import time
 
 log = logging.getLogger(__name__)
 
-import train
-import wave
+from . import train
+from . import wave
 
-import common
-import config
-import sigproc
+from . import common
+from . import config
+from . import sigproc
+from . import stream
+from . import ecc
 
 modem = sigproc.MODEM(config)
 
 
 class Symbol(object):
-    t = np.arange(0, config.Nsym) * config.Ts
-    carrier = [np.exp(2j * np.pi * F * t) for F in modem.freqs]
+    def __init__(self):
+        t = np.arange(0, config.Nsym) * config.Ts
+        self.carrier = [np.exp(2j * np.pi * F * t) for F in modem.freqs]
 
 sym = Symbol()
 
@@ -63,26 +66,7 @@ def modulate(fd, bits):
             break
 
 
-class Reader(object):
-    def __init__(self, fd, size):
-        self.fd = fd
-        self.size = size
-        self.total = 0
-
-    def next(self):
-        block = self.fd.read(self.size)
-        if block:
-            self.total += len(block)
-            return block
-        else:
-            raise StopIteration()
-
-    def __iter__(self):
-        return self
-
-
 def main(args):
-    import ecc
     log.info('Running MODEM @ {:.1f} kbps'.format(modem.modem_bps / 1e3))
 
     # padding audio with silence
@@ -95,7 +79,7 @@ def main(args):
     log.info('%.3f seconds of training audio',
              training_size / wave.bytes_per_second)
 
-    reader = Reader(args.input, 64 << 10)
+    reader = stream.Reader(args.input, bufsize=(64 << 10), eof=True)
     data = itertools.chain.from_iterable(reader)
     encoded = itertools.chain.from_iterable(ecc.encode(data))
     modulate(args.output, bits=common.to_bits(encoded))
@@ -115,7 +99,9 @@ if __name__ == '__main__':
     p = argparse.ArgumentParser()
     p.add_argument('--silence-start', type=float, default=1.0)
     p.add_argument('--silence-stop', type=float, default=1.0)
-    p.add_argument('-i', '--input', type=argparse.FileType('r'), default=sys.stdin)
-    p.add_argument('-o', '--output', type=argparse.FileType('w'), default=sys.stdout)
+    p.add_argument('-i', '--input', type=argparse.FileType('rb'),
+                   default=sys.stdin)
+    p.add_argument('-o', '--output', type=argparse.FileType('wb'),
+                   default=sys.stdout)
     args = p.parse_args()
     main(args)
diff --git a/amodem/sigproc.py b/amodem/sigproc.py
index 270c1fb..91b8f33 100644
--- a/amodem/sigproc.py
+++ b/amodem/sigproc.py
@@ -1,8 +1,8 @@
 import numpy as np
 from numpy import linalg
 
-import common
-from config import Ts, Nsym
+from . import common
+from .config import Ts, Nsym
 
 
 class Filter(object):
diff --git a/amodem/stream.py b/amodem/stream.py
index fc59b93..25844ff 100644
--- a/amodem/stream.py
+++ b/amodem/stream.py
@@ -1,43 +1,57 @@
 import time
-import itertools
+import logging
 
-import common
-import wave
+log = logging.getLogger(__name__)
+
+
+class Timeout(Exception):
+    pass
 
 
 class Reader(object):
 
-    SAMPLES = 4096
-    BUFSIZE = int(SAMPLES * wave.bytes_per_sample)
-    WAIT = 0.1
-    TIMEOUT = 2.0
-
-    def __init__(self, fd):
+    def __init__(self, fd, data_type=None, bufsize=4096,
+                 eof=False, timeout=2.0, wait=0.2):
         self.fd = fd
+        self.data_type = data_type if (data_type is not None) else lambda x: x
+        self.bufsize = bufsize
+        self.eof = eof
+        self.timeout = timeout
+        self.wait = wait
+        self.total = 0
         self.check = None
 
     def __iter__(self):
         return self
 
+    def __next__(self):
+        return self.next()
+
     def next(self):
         block = bytearray()
-        finish_time = time.time() + self.TIMEOUT
+        if self.eof:
+            data = self.fd.read(self.bufsize)
+            if data:
+                self.total += len(data)
+                block.extend(data)
+                return block
+            else:
+                raise StopIteration()
+
+        finish_time = time.time() + self.timeout
         while time.time() <= finish_time:
-            left = self.BUFSIZE - len(block)
+            left = self.bufsize - len(block)
             data = self.fd.read(left)
             if data:
+                self.total += len(data)
                 block.extend(data)
 
-            if len(block) == self.BUFSIZE:
-                values = common.loads(str(block))
+            if len(block) == self.bufsize:
+                values = self.data_type(block)
                 if self.check:
                     self.check(values)
                 return values
 
-            time.sleep(self.WAIT)
+            time.sleep(self.wait)
 
-        raise IOError('timeout')
-
-
-def iread(fd):
-    return itertools.chain.from_iterable(Reader(fd))
+        raise Timeout(self.timeout)
diff --git a/amodem/wave.py b/amodem/wave.py
index 57e47ab..269c66f 100755
--- a/amodem/wave.py
+++ b/amodem/wave.py
@@ -6,7 +6,7 @@ import logging
 
 log = logging.getLogger(__name__)
 
-import config
+from . import config
 Fs = int(config.Fs)  # sampling rate
 
 bits_per_sample = 16
@@ -27,7 +27,7 @@ def record(fname, **kwargs):
 
 
 def launch(*args, **kwargs):
-    args = map(str, args)
+    args = list(map(str, args))
     log.debug('$ %s', ' '.join(args))
     p = sp.Popen(args=args, **kwargs)
     p.stop = lambda: os.kill(p.pid, signal.SIGKILL)
diff --git a/amodem/scripts/auto-calib.sh b/scripts/auto-calib.sh
similarity index 56%
rename from amodem/scripts/auto-calib.sh
rename to scripts/auto-calib.sh
index af47cc2..d97687d 100755
--- a/amodem/scripts/auto-calib.sh
+++ b/scripts/auto-calib.sh
@@ -1,7 +1,7 @@
 #!/bin/bash
 killall -q aplay arecord
-./calib.py send &
+python -m amodem.calib send &
 SENDER_PID=$!
-./calib.py recv
+python -m amodem.calib recv
 
 kill -INT $SENDER_PID
diff --git a/amodem/scripts/profile.sh b/scripts/profile.sh
similarity index 100%
rename from amodem/scripts/profile.sh
rename to scripts/profile.sh
diff --git a/amodem/scripts/test.sh b/scripts/test.sh
similarity index 78%
rename from amodem/scripts/test.sh
rename to scripts/test.sh
index f97bb2b..0e9b640 100755
--- a/amodem/scripts/test.sh
+++ b/scripts/test.sh
@@ -32,20 +32,20 @@ run_src dd if=/dev/urandom of=$TEST_DIR/data.send bs=125kB count=1 status=none
 SRC_HASH=`run_src sha256sum $TEST_DIR/data.send`
 
 # modulate data into audio file
-run_src "./send.py <$TEST_DIR/data.send >$TEST_DIR/audio.send"
+run_src "python -m amodem.send -i $TEST_DIR/data.send -o $TEST_DIR/audio.send"
 
 # stop old recording and start a new one
 run_src killall -q aplay || true
 run_dst killall -q arecord || true
 
-run_dst "./wave.py record $TEST_DIR/audio.recv" &
+run_dst "python -m amodem.wave record $TEST_DIR/audio.recv" &
 sleep 1  # let audio.recv be filled
 
 # play the modulated data
-run_src ./wave.py play   $TEST_DIR/audio.send &
+run_src "python -m amodem.wave play   $TEST_DIR/audio.send" &
 
 # start the receiever
-run_dst "./recv.py <$TEST_DIR/audio.recv >$TEST_DIR/data.recv"
+run_dst "python -m amodem.recv -i $TEST_DIR/audio.recv -o $TEST_DIR/data.recv"
 
 # stop recording after playing is over
 run_src killall -q aplay || true
diff --git a/tests/test_common.py b/tests/test_common.py
index c5e32aa..7858fec 100644
--- a/tests/test_common.py
+++ b/tests/test_common.py
@@ -25,13 +25,13 @@ def test_iterate():
 def test_split():
     L = [(i*2, i*2+1) for i in range(10)]
     iters = common.split(L, n=2)
-    assert zip(*iters) == L
+    assert list(zip(*iters)) == L
 
     for i in [0, 1]:
         iters = common.split(L, n=2)
-        iters[i].next()
+        next(iters[i])
         try:
-            iters[i].next()
+            next(iters[i])
             assert False
         except IndexError as e:
             assert e.args == (i,)
@@ -43,8 +43,8 @@ def test_icapture():
     z = []
     for i in common.icapture(x, result=y):
         z.append(i)
-    assert x == y
-    assert x == z
+    assert list(x) == y
+    assert list(x) == z
 
 
 def test_dumps_loads():
diff --git a/tests/test_full.py b/tests/test_full.py
index 564e8af..3c1a533 100644
--- a/tests/test_full.py
+++ b/tests/test_full.py
@@ -1,5 +1,9 @@
 import os
-from cStringIO import StringIO
+try:
+    from cStringIO import StringIO as BytesIO
+except ImportError:
+    from io import BytesIO  # Python 3
+
 import numpy as np
 
 from amodem import send
@@ -10,40 +14,48 @@ import logging
 logging.basicConfig(level=logging.DEBUG,
                     format='%(asctime)s %(levelname)-12s %(message)s')
 
+
 class Args(object):
     def __init__(self, **kwargs):
         self.__dict__.update(kwargs)
 
+
 def run(size, chan):
     tx_data = os.urandom(size)
-    tx_audio = StringIO()
-    send.main(Args(silence_start=1, silence_stop=1, input=StringIO(tx_data), output=tx_audio))
+    tx_audio = BytesIO()
+    send.main(Args(silence_start=1, silence_stop=1,
+              input=BytesIO(tx_data), output=tx_audio))
 
     data = tx_audio.getvalue()
     data = common.loads(data)
     data = chan(data)
     data = common.dumps(data * 1j)
-    rx_audio = StringIO(data)
+    rx_audio = BytesIO(data)
 
-    rx_data = StringIO()
+    rx_data = BytesIO()
     recv.main(Args(skip=100, input=rx_audio, output=rx_data))
     rx_data = rx_data.getvalue()
 
     assert rx_data == tx_data
 
+
 def test_small():
     run(1024, lambda x: x)
 
+
 def test_large():
     run(54321, lambda x: x)
 
+
 def test_attenuation():
     run(5120, lambda x: x * 0.1)
 
+
 def test_low_noise():
     r = np.random.RandomState(seed=0)
     run(5120, lambda x: x + r.normal(size=len(x), scale=0.0001))
 
+
 def test_medium_noise():
     r = np.random.RandomState(seed=0)
     run(5120, lambda x: x + r.normal(size=len(x), scale=0.001))
diff --git a/tests/test_stream.py b/tests/test_stream.py
index 5dbbcf4..8805bd1 100644
--- a/tests/test_stream.py
+++ b/tests/test_stream.py
@@ -1,14 +1,14 @@
 from amodem import stream
 import subprocess as sp
 
-script = r"""
+script = br"""
 import sys
 import time
 import os
 
 while True:
     time.sleep(0.1)
-    sys.stdout.write(b'\x00' * 6400)
+    sys.stdout.write('\x00' * 6400)
     sys.stderr.write('.')
 """
 
@@ -19,17 +19,17 @@ def test_read():
     p.stdin.close()
     f = stream.Reader(p.stdout)
 
-    result = zip(range(10), f)
+    result = list(zip(range(10), f))
     p.kill()
 
     j = 0
     for i, buf in result:
         assert i == j
-        assert len(buf) == f.SAMPLES
+        assert len(buf) == f.bufsize
         j += 1
 
     try:
         for buf in f:
             pass
-    except IOError as e:
-        assert str(e) == 'timeout'
+    except stream.Timeout as e:
+        assert e.args == (f.timeout,)