user28: As a developer building an application, what are different way to access the Cardano network?

user235: Generally, there are several options you could pursue.

Start a stake pool on test-net and then launch one on main-net.
How to build a Cardano Stake Pool.
Get involved with project catalyst. Offer feedback and input to projects that interest you. Try to get involved with a team that has promising ideas. Offer your services where you can fit in.
Project Catalyst Ideascale.
Try building smart contracts using Marlowe. Marlowe Playground.
Mint your own native token on Cardano. FAQ : Native Tokens (Cardano’s Multi-Asset Support Feature)
Follow along with the videos for the Plutus Pioneers Program and learn to write smart contracts in Cardano's on chain programming language. Plutus Pioneers Program on YouTube
Figure out how to mint some NFTs...
Integration with Atala Prism for identity and certification. Atala PRISM

I'm sure there are lots of other possibilities that I haven't heard of or considered. There is no shortage of room to explore for a developer.

user67: There are also ways to use services where you can make API requests to interact with the Cardano blockchain. (without the need to run your own cardano-node)
You could for example sign in on Blockfrost with your GitHub account. No registration required. Enter a project name and select Cardano mainnet or Cardano testnet, depending on your needs.
After generating your API KEY you can send your first request to get data for example about the latest epoch:
curl -H 'project_id: 1234567890' https://cardano-mainnet.blockfrost.io/api/v0/epochs/latest
And you will get a response in JSON format similar to this:
{ "epoch": 225,   "start_time": 1603403091, "end_time": 1603835086, "first_block_time": 1603403092, "last_block_time": 1603835084, "block_count": 21298, "tx_count": 17856, "output": "7849943934049314", "fees": "4203312194", "active_stake": "784953934049314" }
Visit docs.blockfrost.io to see the complete API documentation.

user38: If you use Nix or NixOs, it is rather straightforward: Build the code for a cardano node using nix (link to current documentation)
Duplicating the official documentation:
git clone https://github.com/input-output-hk/cardano-node
cd cardano-node
nix-build -A scripts.mainnet.node -o mainnet-node-local
./mainnet-node-local

This will run a cardano node on the mainnet.
Then you can also build and use the CLI tool to interact with the cardano network.

In the provided solution above, if you don't want to compile GHC which can take a long time, IOHK provides many binaries that are pre-compiled for you: lots of time gained ! So don't hesitate to use their nix binary cache
In NixOS, I currently set it this way:
# configuration.nix
{ config, pkgs, ... }:
{
  # ... all the rest of the configuration of the server

  # iohk binary caches
  nix = 
  {
    binaryCaches          = [ "https://hydra.iohk.io" "https://iohk.cachix.org" ];
    binaryCachePublicKeys = [ "hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=" "iohk.cachix.org-1:DpRUyj7h7V830dp/i6Nti+NEO2/nhblbov/8MW7Rqoo=" ];
  };
}


28: <p>As a developer building an application, what are different way to access the Cardano network?</p>
 235: <p>Generally, there are several options you could pursue.</p>
<ul>
<li>Start a stake pool on test-net and then launch one on main-net.
<a href="https://www.coincashew.com/coins/overview-ada/guide-how-to-build-a-haskell-stakepool-node" rel="noreferrer">How to build a Cardano Stake Pool.</a></li>
<li>Get involved with project catalyst. Offer feedback and input to projects that interest you. Try to get involved with a team that has promising ideas. Offer your services where you can fit in.
<a href="https://cardano.ideascale.com/" rel="noreferrer">Project Catalyst Ideascale.</a></li>
<li>Try building smart contracts using Marlowe. <a href="https://alpha.marlowe.iohkdev.io/#/" rel="noreferrer">Marlowe Playground.</a></li>
<li>Mint your own native token on Cardano. <a href="https://cardano-ledger.readthedocs.io/en/latest/explanations/faq.html" rel="noreferrer">FAQ : Native Tokens (Cardano’s Multi-Asset Support Feature)</a></li>
<li>Follow along with the videos for the Plutus Pioneers Program and learn to write smart contracts in Cardano's on chain programming language. <a href="https://youtube.com/playlist?list=PLK8ah7DzglhhJzuiz7X33UCHSTYPB-8Jt" rel="noreferrer">Plutus Pioneers Program on YouTube</a></li>
<li>Figure out how to mint some NFTs...</li>
<li>Integration with Atala Prism for identity and certification. <a href="https://atalaprism.io/app" rel="noreferrer">Atala PRISM</a></li>
</ul>
<p>I'm sure there are lots of other possibilities that I haven't heard of or considered. There is no shortage of room to explore for a developer.</p>
 67: <p>There are also ways to use services where you can make API requests to interact with the Cardano blockchain. (without the need to run your own cardano-node)</p>
<p>You could for example <a href="https://blockfrost.io/auth/signin" rel="noreferrer">sign in on Blockfrost</a> with your GitHub account. No registration required. Enter a project name and select Cardano mainnet or Cardano testnet, depending on your needs.</p>
<p>After generating your <code>API KEY</code> you can send your first request to get data for example about the latest epoch:</p>
<p><code>curl -H 'project_id: 1234567890' https://cardano-mainnet.blockfrost.io/api/v0/epochs/latest</code></p>
<p>And you will get a response in JSON format similar to this:</p>
<p><code>{ &quot;epoch&quot;: 225,   &quot;start_time&quot;: 1603403091, &quot;end_time&quot;: 1603835086, &quot;first_block_time&quot;: 1603403092, &quot;last_block_time&quot;: 1603835084, &quot;block_count&quot;: 21298, &quot;tx_count&quot;: 17856, &quot;output&quot;: &quot;7849943934049314&quot;, &quot;fees&quot;: &quot;4203312194&quot;, &quot;active_stake&quot;: &quot;784953934049314&quot; }</code></p>
<p>Visit <a href="https://docs.blockfrost.io" rel="noreferrer">docs.blockfrost.io</a> to see the complete API documentation.</p>
 38: <p>If you use Nix or NixOs, it is rather straightforward: <a href="https://docs.cardano.org/projects/cardano-node/en/latest/getting-started/building-the-node-using-nix.html" rel="noreferrer">Build the code for a cardano node using nix</a> (link to current documentation)</p>
<p>Duplicating the official documentation:</p>
<pre><code>git clone https://github.com/input-output-hk/cardano-node
cd cardano-node
nix-build -A scripts.mainnet.node -o mainnet-node-local
./mainnet-node-local
</code></pre>
<p>This will run a cardano node on the mainnet.</p>
<p>Then you can also build and use the CLI tool to interact with the cardano network.</p>
<hr>
<p>In the provided solution above, if you don't want to compile GHC which can take a long time, IOHK provides many binaries that are pre-compiled for you: lots of time gained ! So don't hesitate to use their nix binary cache</p>
<p>In NixOS, I currently set it this way:</p>
<pre><code># configuration.nix
{ config, pkgs, ... }:
{
  # ... all the rest of the configuration of the server

  # iohk binary caches
  nix = 
  {
    binaryCaches          = [ &quot;https://hydra.iohk.io&quot; &quot;https://iohk.cachix.org&quot; ];
    binaryCachePublicKeys = [ &quot;hydra.iohk.io:f/Ea+s+dFdN+3Y/G+FDgSq+a5NEWhJGzdjvKNGv0/EQ=&quot; &quot;iohk.cachix.org-1:DpRUyj7h7V830dp/i6Nti+NEO2/nhblbov/8MW7Rqoo=&quot; ];
  };
}
</code></pre>
