user24926: After a node receives an inv message, you can get the data for each tx/block hash using getdata:

getdata - Request a single block or transaction by hash.

So if you can only get one tx or block at a time, what's the purpose of having a field in the getdata message for the number of entries you are requesting?

Field Size  Description   Data type   Comments
----------  ------------  ----------  -------------
?           count         var_int     Number of inventory entries
36x?        inventory     inv_vect[]  Inventory vectors



https://wiki.bitcoin.com/w/Network#Messages
https://en.bitcoin.it/wiki/Protocol_documentation#getdata

user20835: The documentation you are linking too is wrong, the bitcoin developer reference indicates you can send multiple inventories inside of a GetData message. 

24926: <p>After a node receives an <code>inv</code> message, you can get the data for each tx/block hash using <code>getdata</code>:</p>

<blockquote>
  <p>getdata - Request a single block or transaction by hash.</p>
</blockquote>

<p>So if you can only get one tx or block at a time, what's the purpose of having a field in the <code>getdata</code> message for the <em>number of entries</em> you are requesting?</p>

<blockquote>
<pre><code>Field Size  Description   Data type   Comments
----------  ------------  ----------  -------------
?           count         var_int     Number of inventory entries
36x?        inventory     inv_vect[]  Inventory vectors
</code></pre>
</blockquote>

<hr>

<p><a href="https://wiki.bitcoin.com/w/Network#Messages" rel="nofollow">https://wiki.bitcoin.com/w/Network#Messages</a>
<a href="https://en.bitcoin.it/wiki/Protocol_documentation#getdata" rel="nofollow">https://en.bitcoin.it/wiki/Protocol_documentation#getdata</a></p>
 20835: <p>The documentation you are linking too is wrong, the <a href="https://bitcoin.org/en/developer-reference#getdata" rel="nofollow">bitcoin developer reference</a> indicates you can send multiple inventories inside of a <code>GetData</code> message. </p>
