# Introduction

The RPC service is the link between the SDK and the nodes on the chain.

Currently, the official RPC service for testing and production environments is provided, and developers can choose which one to use when using the SDK.

TestNet:

Account Chain : test1.thinkiumrpc.net chainId: 60001

PoS Chain : test2.thinkiumrpc.net chainId: 60002

Business Chain : test103.thinkiumrpc.net chainId : 60103

Cross Chain: test.thinkiumrpc.net

MainNet:

Account Chain : proxy1.thinkiumrpc.net chainId: 70001

PoS Chain : proxy2.thinkiumrpc.net chainId: 70002

Business Chain : proxy103.thinkiumrpc.net chainId : 70103

Cross Chain: proxy.thinkiumrpc.net