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<div class="title">Chapter 8: Threads with libssh </div> </div>
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<div class="textblock"><h1><a class="anchor" id="threads_with_libssh"></a>
How to use libssh with threads</h1>
<p>libssh may be used in multithreaded applications, but under several conditions :</p><ul>
<li>Your system must support libpthread or, in Windows environment, CriticalSection based mutex control.</li>
<li>Since version 0.8.0, threads initialization is called automatically in the library constructor if libssh is dynamically linked. This means it is no longer necessary to call <a class="el" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures. ">ssh_init()</a>/ssh_finalize().</li>
<li>If libssh is statically linked, threading must be initialized by calling <a class="el" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures. ">ssh_init()</a> before using any of libssh provided functions. This initialization must be done outside of any threading context. Don't forget to call <a class="el" href="group__libssh.html#ga94a851d00248acde9cd7da084b491242" title="Finalize and cleanup all libssh and cryptographic data structures. ">ssh_finalize()</a> to avoid memory leak</li>
<li>At all times, you may use different sessions inside threads, make parallel connections, read/write on different sessions and so on. You <em>cannot</em> use a single session (or channels for a single session) in several threads at the same time. This will most likely lead to internal state corruption. This limitation is being worked out and will maybe disappear later.</li>
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<h2><a class="anchor" id="threads_init"></a>
Initialization of threads</h2>
<p>Since version 0.8.0, it is no longer necessary to call <a class="el" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures. ">ssh_init()</a>/ssh_finalize() if libssh is dynamically linked.</p>
<p>If libssh is statically linked, call <a class="el" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures. ">ssh_init()</a> before using any of libssh provided functions.</p>
<h2><a class="anchor" id="threads_pthread"></a>
Using libpthread with libssh</h2>
<p>Since version 0.8.0, libpthread is the default threads library used by libssh.</p>
<p>To use libpthread, simply link it to you application.</p>
<p>If you are using libssh statically linked, don't forget to call <a class="el" href="group__libssh.html#ga3ebf8d6920e563f3b032e3cd5277598e" title="Initialize global cryptographic data structures. ">ssh_init()</a> before using any of libssh provided functions (and <a class="el" href="group__libssh.html#ga94a851d00248acde9cd7da084b491242" title="Finalize and cleanup all libssh and cryptographic data structures. ">ssh_finalize()</a> in the end).</p>
<h2><a class="anchor" id="threads_other"></a>
Using another threading library</h2>
<p>Since version 0.8.0, libssh does not support custom threading libraries. The change makes sense since the newer versions for libcrypto (OpenSSL) and libgcrypt don't support custom threading libraries.</p>
<p>The default used threading library is libpthread. Alternatively, in Windows environment, CriticalSection based mutex control can be used.</p>
<p>If your system does not support libpthread nor CriticalSection based mutex control, unfortunately, you cannot use libssh in multithreaded scenarios.</p>
<p>Good luck ! </p>
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