trying to follow whats going on here...

you're generating terrain using a random number seed.

you start with a tile at 0,0.

but when you add tiles around it, they don't "connect" correctly, despite having an "allowable adjacency" table ?

first thing... are the allowable adjacency tables in the client and server the same? a typo in one would cause the problem you're getting, IE client and server generate different tiles from same seed.

You need to make the generation more hierarchial, so that the "chunks" can be placed in whatever way you feel like. Inside each of those chunks, you now have limited beach-y stuff to watery areas, and city stuff to city areas etc.

So.

[Water, Shore, Land]

**Water:[Oil rig, Sea, Rocky island]

**Shore:[Beach, Harbor, Seaside buildings]

**Land:[Habitated area, Nonhabitated area]

****Habitated area:[City, Village, Farmland]

****Nonhabitated area:[Jungle, Trees, Mountain, Plain]

Each chunk at a particular level should be able to transfer to any other chunk at that level. When picking out the chunks in the level below, take the neighbors at the upper level into account.

For example, you have Shore and Land touch each other. So, when generating Land, you try to place habitated area near that edge, and nonhabitated area away from that edge.

Or if you have Habitated and nonhabitated area next to each other, you try to place Mountain of nonhabitated area away from the shared edge with habitated area.

This would probably create smooth transitions and keep everything logical, and possibly make the world look less ugly. Its a big more complex though.

Random map generation with cohesive features flow of tile types that make sense

I did this before and the way you do it is to grow the features

You place seeds that terrain types grow out from and rules that arbitrate conflicting types

Water features usuall are a key determining factor so you probably build those first ocean areas and rivers (rivers travel in a given direction doing some random wandering )

Then heights like mountains that grow out from a few scattered start points (and have a change to down grade to hills before shifting to flat (and stopping)

Next certain plant ecology terrain has restrictions like jungle must be near water high mountaisn dont have trees abut lower ones might

beaches (if you have them) are around edges of ocean

desert scrub is on flat away from water

etc.. for the rules (I recall I did an 'influence map' for nearness to water when it had to reflect more than simple adjacency)

Depending on your game mechanics you may have to reprocess the simple 'grown' map to make adaquate play area - randomly flattening areas or forcing an ocean that takes up too much of the map to be smaller etc....