Is there an alternative for GetComponent in Godot as I need to access other components?
Here's what we have in Unity:
socket = GetComponent<SocketIOComponent>();
I'm trying to convert Unity C# files to Godot C#.
You can use the GetNode method and cast the result to type of the node. You'll need to specify NodePath since Godot uses String paths to specify references to other nodes instead of the more complex system used by Unity under the hood.
How Godot handles composition is a bit different from Unity. In Unity you might have a single GameObject with multiple components, but to achieve the same in Godot you would have a parent Node with multiple child nodes that work like components would in Unity. To refer to these nodes ("components") from parent one would do so with GetNode and specify the path to the node and cast it to the type of the node, i.e., RigidBody.
Probably the most Unityish approach you could do is something that's very similar to dragging component references to public fields on components. In Godot you can do something like that by exporting NodePath variables which allow you to specify a path to a specific node in the node hierarchy and then use that with GetNode to get the actual "component".