---
title: "proto_bin Module"
description: "The **proto_bin** module is a transport module which implements Binary Interface TCP-based communication."
---

## Admin Guide


### Overview


The **proto_bin** module is a
transport module which implements Binary Interface TCP-based communication. It does
not handle TCP connections management, but only offers higher-level
primitives to read and write BIN messages over TCP. It calls registered
callback functions for every complete message received.


Once loaded, you will be able to define BIN listeners in your
configuration file by adding their IP and, optionally, a listening port,
similar to this example:

```opensips
...
socket = bin:127.0.0.1 		# change the listening IP
socket = bin:127.0.0.1:5080	# change the listening IP and port
...
```


### Dependencies


#### OpenSIPS Modules


The following modules must be loaded before this module:


- *None*.


#### External Libraries or Applications


The following libraries or applications must be installed before
running OpenSIPS with this module loaded:


- *None*.


### Exported Parameters


#### bin_port (integer)


The default port to be used by all TCP listeners.


*Default value is 5555.*


```c title="Set bin_port parameter"
...
modparam("proto_bin", "bin_port", 6666)
...
```


#### bin_send_timeout (integer)


Time in milliseconds after a TCP connection will be closed if it is
not available for blocking writing in this interval (and OpenSIPS wants
to send something on it).


*Default value is 100 ms.*


```opensips title="Set bin_send_timeout parameter"
...
modparam("proto_bin", "bin_send_timeout", 200)
...
```


#### bin_max_msg_chunks (integer)


The maximum number of chunks in which a BIN message is expected to
arrive via TCP. If a received packet is more fragmented than this,
the connection is dropped (either the connection is very
overloaded and this leads to high fragmentation - or we are the
victim of an ongoing attack where the attacker is sending very
fragmented traffic in order to decrease server performance).


*Default value is 32.*


```opensips title="Set bin_max_msg_chunks parameter"
...
modparam("proto_bin", "bin_max_msg_chunks", 8)
...
```


#### bin_async (integer)


Specifies whether the TCP connect and write operations should be
done in an asynchronous mode (non-blocking connect and
write) or not. If disabled, OpenSIPS will block and wait for TCP
operations like connect and write.


*Default value is 1 (enabled).*


```opensips title="Set bin_async parameter"
...
modparam("proto_bin", "bin_async", 0)
...
```


#### bin_async_max_postponed_chunks (integer)


If *bin_async* is enabled, this specifies the
maximum number of BIN messages that can be stashed for later/async
writing. If the connection pending writes exceed this number, the
connection will be marked as broken and dropped.


*Default value is 1024.*


```opensips title="Set bin_async_max_postponed_chunks parameter"
...
modparam("proto_bin", "bin_async_max_postponed_chunks", 1024)
...
```


#### bin_async_local_write_timeout (integer)


If *bin_async* is enabled, this specifies the
number of milliseconds that a write op will be tried in blocking
mode (optimization). If the write operation lasts more than this,
the write will go to async mode and will be passed to bin MAIN for
polling.


*Default value is 10 ms.*


```opensips title="Set bin_async_local_write_timeout parameter"
...
modparam("proto_bin", "tcp_async_local_write_timeout", 100)
...
```
<!-- CONTRIBUTORS -->

### License

All documentation files (i.e. .md extension) are licensed under the Creative Common License 4.0
