| Daemonization |
| ------------- |
| |
| There's a helper api lws_daemonize built by default that does everything you |
| need to daemonize well, including creating a lock file. If you're making |
| what's basically a daemon, just call this early in your init to fork to a |
| headless background process and exit the starting process. |
| |
| Notice stdout, stderr, stdin are all redirected to /dev/null to enforce your |
| daemon is headless, so you'll need to sort out alternative logging, by, eg, |
| syslog. |
| |
| |
| Maximum number of connections |
| ----------------------------- |
| |
| The maximum number of connections the library can deal with is decided when |
| it starts by querying the OS to find out how many file descriptors it is |
| allowed to open (1024 on Fedora for example). It then allocates arrays that |
| allow up to that many connections, minus whatever other file descriptors are |
| in use by the user code. |
| |
| If you want to restrict that allocation, or increase it, you can use ulimit or |
| similar to change the avaiable number of file descriptors, and when restarted |
| libwebsockets will adapt accordingly. |
| |
| |
| Procedure for sending data from other threads or process contexts |
| ----------------------------------------------------------------- |
| |
| Libwebsockets is carefully designed to work with no blocking in a single thread. |
| In some cases where you will add libwebsockets to something else that uses the |
| same single thread approach, you can so a safe implementation by combining the |
| poll() loops as described in "External Polling loop support" below. |
| |
| In other cases, you find you have asynchronous events coming from other thread |
| or process contexts and there's not much you can do about it. If you just try |
| to randomly send, or broadcast using libwebsockets_broadcast() from these other |
| places things will blow up either quickly or when the events on the two threads |
| interefere with each other. It's not legal to do this. |
| |
| For those situations, you can use libwebsockets_broadcast_foreign(). This |
| serializes the data you're sending using a private, per-protocol socket, so the |
| service thread picks it up when it's ready, and it is serviced from the service |
| thread context only. |
| |
| |
| Fragmented messages |
| ------------------- |
| |
| To support fragmented messages you need to check for the final |
| frame of a message with libwebsocket_is_final_fragment. This |
| check can be combined with libwebsockets_remaining_packet_payload |
| to gather the whole contents of a message, eg: |
| |
| case LWS_CALLBACK_RECEIVE: |
| { |
| Client * const client = (Client *)user; |
| const size_t remaining = libwebsockets_remaining_packet_payload(wsi); |
| |
| if (!remaining && libwebsocket_is_final_fragment(wsi)) { |
| if (client->HasFragments()) { |
| client->AppendMessageFragment(in, len, 0); |
| in = (void *)client->GetMessage(); |
| len = client->GetMessageLength(); |
| } |
| |
| client->ProcessMessage((char *)in, len, wsi); |
| client->ResetMessage(); |
| } else |
| client->AppendMessageFragment(in, len, remaining); |
| } |
| break; |
| |
| The test app llibwebsockets-test-fraggle sources also show how to |
| deal with fragmented messages. |
| |
| |
| Debug Logging |
| ------------- |
| |
| Also using lws_set_log_level api you may provide a custom callback to actually |
| emit the log string. By default, this points to an internal emit function |
| that sends to stderr. Setting it to NULL leaves it as it is instead. |
| |
| A helper function lwsl_emit_syslog() is exported from the library to simplify |
| logging to syslog. You still need to use setlogmask, openlog and closelog |
| in your user code. |
| |
| The logging apis are made available for user code. |
| |
| lwsl_err(...) |
| lwsl_warn(...) |
| lwsl_notice(...) |
| lwsl_info(...) |
| lwsl_debug(...) |
| |
| The difference between notice and info is that notice will be logged by default |
| whereas info is ignored by default. |
| |
| |
| External Polling Loop support |
| ----------------------------- |
| |
| libwebsockets maintains an internal poll() array for all of its |
| sockets, but you can instead integrate the sockets into an |
| external polling array. That's needed if libwebsockets will |
| cooperate with an existing poll array maintained by another |
| server. |
| |
| Four callbacks LWS_CALLBACK_ADD_POLL_FD, LWS_CALLBACK_DEL_POLL_FD, |
| LWS_CALLBACK_SET_MODE_POLL_FD and LWS_CALLBACK_CLEAR_MODE_POLL_FD |
| appear in the callback for protocol 0 and allow interface code to |
| manage socket descriptors in other poll loops. |
| |
| |