as write_request handles bytes, just use this instead of to_bytes...

aiosocks/protocols.py

@@ -319,8 +319,8 @@ class Socks5Protocol(BaseSocksProtocol):
             )
 
         if chosen_auth[1] == c.SOCKS5_AUTH_UNAME_PWD:
-            req = [0x01, len(self._auth.login).to_bytes(1, 'big'), self._auth.login,
-                   len(self._auth.password).to_bytes(1, 'big'), self._auth.password]
+            req = [0x01, len(self._auth.login), self._auth.login,
+                   len(self._auth.password), self._auth.password]
             self.write_request(req)
 
             auth_status = await self.read_response(2)
@@ -361,7 +361,7 @@ class Socks5Protocol(BaseSocksProtocol):
         # it's not an IP number, so it's probably a DNS name.
         if self._remote_resolve:
             host_bytes = host.encode('idna')
-            req = [c.SOCKS5_ATYP_DOMAIN, len(host_bytes).to_bytes(1, 'big'),
+            req = [c.SOCKS5_ATYP_DOMAIN, len(host_bytes),
                    host_bytes, port_bytes]
         else:
             family, host_bytes = await self._get_dst_addr()

tests/test_protocols.py

@@ -566,7 +566,7 @@ async def test_socks5_build_dst_addr_domain_with_remote_resolve(loop):
     proto = make_socks5(loop)
     dst_req, resolved = await proto.build_dst_address('python.org' * 20, 80)
 
-    assert dst_req == [0x03, b'\xc8', b'python.org' * 20, b'\x00P']
+    assert dst_req == [0x03, 200, b'python.org' * 20, b'\x00P']
     assert resolved == ('python.org' * 20, 80)