Is conveying information by means of bets legal in poker?

In contract bridge, players communicate the information within a hand by the bids and play, which must be known to be opponents.

In poker, is it legal for players to openly communicate the content of the hands, using codes (e.g. bet sizes) which must be disclosed to opponents?

I mean.... are you asking if it's legal for players to collude in this way?, no,

of course once you notice what they're doing they're also signalling to you too...,

is it legal for a player to signal strength or weakness to an opponent through bet sizing?, sure👍

Sharing information through betting in poker is called collusion and is illegal. Violating the competitive and ethical rules of the game, poker is an individual game where each player should act only in their own self-interest. Sharing information through betting patterns (such as using specific values to indicate the strength of a hand to a partner) is considered a form of cheating to gain an unfair advantage over other players.

No it would not be legal as it's collusion which is strictly forbidden.

It's the same as any other means of sharing information about your hand to some players to the determent of others.
- it is just not allowed. All players should operate with the same level (or lack) of information to prevent an unfair advantage.

You could invent 'Contract' Poker, but the whole table would know your hand when via your signal, so how's that going to work?

It would be (academically) interesting to devise a hand coding system via bet sizes. I have been on 'shoddy' poker sites in the past that would allow you to enter a bet with a whole string of numbers after the decimal point, eg. 25.0125 (I always used to laugh at it and try and leave my unaware opponents with 0.0001 chips when I stacked them in cash games ). With this flaw it would be easy to encode your hand into the decimal part, but God help you if the site or (even worse) your opponents figured out what you were doing. Other simpler codes using the whole number of chips you bet could be devised but they would be so transparent they'd soon be discovered, then counter exploited (or get you banned).

I think it's illegal, because there is money involved, so there should be no transmission through gambling.

It should not be in any way but every page is also included in the rules... you have to report it if there is one in the right place

In bridge, communication is allowed and regulated.

In poker, any intentional communication about a hand —

even if it is “public,”
even if it uses visible bets —

is illegal if there is a prior agreement.

of course its not