In CS and I assume SE, conferences are a good way to meet people with similar interests. Especially specialized conferences in your specific field. Generally, I've found that people welcome collaboration and that such relationships can be long lasting and productive. Likewise, there are workshops that are a bit more intense than conferences, but more valuable.
But you need to build them slowly enough that people become comfortable with your work and with your participation.
I once joined a collaborative community just by asking one of the founders if she had "thought of X", which was related to her talk. She said no, but that I should write it up.
Cold emails probably aren't a good way to introduce yourself, especially if you flood the receiver with your work. But an introduction by email, expressing interest in the other person's work can help, especially if you make it obvious you know something about it.
If you want to get someone interested in your work, you can make an introduction and mention that you are working on a paper on "topic X" that you are willing to share. If they are interested, they will respond.
As to industry experience and interest, it will vary with the person. Some won't be very interested at all, but some will be, and you can often discern that from the papers they publish.
If you are a student, try to join the collaboration circle of your advisor or other related faculty members. You can get access to a lot of experience and wind up, over time, as an important contributor. Many departments will have a few research seminars that you can join. You can also found one if there is enough synergy with students and faculty. This works best at larger places, of course. But if you are at a small place in a city/region with a lot of universities, you can try to get a seminar going with members from more than one institution.
Also, respond appropriately to requests made of you. It will take some time and effort, but it can be worth it. But think long term.
But, online and part-time programs offer many fewer opportunities as it takes time and effort. I'm especially skeptical of online programs as they offer very little contact with faculty. Part time can work but only if you are willing to work very intensively.