You may use various methods to test getting market prices by using WebSocket.
The most well-known methods are telsocket or wscat.

When you use wscat

$ npm install -g wscat
$ wscat -c wss://sg-api.upbit.com/websocket/v1
connected (press CTRL+C to quit)
$ npm install -g wscat
$ wscat -c wss://id-api.upbit.com/websocket/v1
connected (press CTRL+C to quit)
$ npm install -g wscat
$ wscat -c wss://th-api.upbit.com/websocket/v1
connected (press CTRL+C to quit)

When you use telsocket

$ telsocket -url wss://sg-api.upbit.com/websocket/v1
Connected!
$ telsocket -url wss://id-api.upbit.com/websocket/v1
Connected!
$ telsocket -url wss://th-api.upbit.com/websocket/v1
Connected!

If you want real-time information on the SGD-Bitcoin (SGD-BTC) market, you can make the request as follows.

$ telsocket -url wss://sg-api.upbit.com/websocket/v1
Connected!
> [{"ticket":"test"},{"type":"ticker","codes":["SGD-BTC"]}]
{"market":"SGD-BTC","opening_price":8450000.00000000,"high_price":8679000.00000000,"low_price":8445000.00000000,"trade_price":8629000.0,"prev_closing_price":8450000.00000000,"acc_trade_price":105514711074.18726000,"change":"RISE","change_price":179000.00000000,"signed_change_price":179000.00000000,"change_rate":0.0211834320,"signed_change_rate":0.0211834320,"ask_bid":"ASK","trade_volume":0.0105675,"acc_trade_volume":12312.36058857,"trade_date":"20180418","trade_time":"100729","trade_timestamp":1524046049000,"acc_ask_volume":5703.42273172,"acc_bid_volume":6608.93785685,"highest_52_week_price":28885000.00000000,"highest_52_week_date":"2018-01-06","lowest_52_week_price":3286000.00000000,"lowest_52_week_date":"2017-09-15","trade_status":"ACTIVE","market_state":"ACTIVE","market_state_for_ios":"ACTIVE","is_trading_suspended":false,"delisting_date":null,"market_warning":"NONE","timestamp":1524046049766,"acc_trade_price_24h":55330325803.78210000,"acc_trade_volume_24h":6448.96200341}
 {"market":"SGD-BTC","opening_price":8450000.00000000,"high_price":8679000.00000000,"low_price":8445000.00000000,"trade_price":8629000.0,"prev_closing_price":8450000.00000000,"acc_trade_price":105515441503.850220000,"change":"RISE","change_price":179000.00000000,"signed_change_price":179000.00000000,"change_rate":0.0211834320,"signed_change_rate":0.0211834320,"ask_bid":"ASK","trade_volume":0.08464824,"acc_trade_volume":12312.44523681,"trade_date":"20180418","trade_time":"100730","trade_timestamp":1524046050000,"acc_ask_volume":5703.50737996,"acc_bid_volume":6608.93785685,"highest_52_week_price":28885000.00000000,"highest_52_week_date":"2018-01-06","lowest_52_week_price":3286000.00000000,"lowest_52_week_date":"2017-09-15","trade_status":"ACTIVE","market_state":"ACTIVE","market_state_for_ios":"ACTIVE","is_trading_suspended":false,"delisting_date":null,"market_warning":"NONE","timestamp":1524046050758,"acc_trade_price_24h":55330325803.78210000,"acc_trade_volume_24h":6448.96200341}
...
$ telsocket -url wss://id-api.upbit.com/websocket/v1
Connected!
> [{"ticket":"test"},{"type":"ticker","codes":["BTC-ETH"]}]
{"type":"ticker","code":"BTC-ETH","opening_price":0.02040727,"high_price":0.02080000,"low_price":0.02005003,"trade_price":0.02033990,"prev_closing_price":0.02040727,"acc_trade_price":28.94601828,"change":"FALL","change_price":0.00006737,"signed_change_price":-0.00006737,"change_rate":0.0033012745,"signed_change_rate":-0.0033012745,"ask_bid":"BID","trade_volume":0.14347633,"acc_trade_volume":1424.31382618,"trade_date":"20191125","trade_time":"092304","trade_timestamp":1574673784000,"acc_ask_volume":1092.53436480,"acc_bid_volume":331.77946138,"highest_52_week_price":0.04167024,"highest_52_week_date":"2019-01-05","lowest_52_week_price":0.01614901,"lowest_52_week_date":"2019-09-06","trade_status":null,"market_state":"ACTIVE","market_state_for_ios":null,"is_trading_suspended":false,"delisting_date":null,"market_warning":"NONE","timestamp":1574673784242,"acc_trade_price_24h":86.0899596010439837,"acc_trade_volume_24h":4209.39183766,"stream_type":"SNAPSHOT"}
{"type":"ticker","code":"BTC-ETH","opening_price":0.02040727,"high_price":0.02080000,"low_price":0.02005003,"trade_price":0.02033990,"prev_closing_price":0.02040727,"acc_trade_price":28.94601828,"change":"FALL","change_price":0.00006737,"signed_change_price":-0.00006737,"change_rate":0.0033012745,"signed_change_rate":-0.0033012745,"ask_bid":"BID","trade_volume":0.14347633,"acc_trade_volume":1424.31382618,"trade_date":"20191125","trade_time":"092304","trade_timestamp":1574673784000,"acc_ask_volume":1092.53436480,"acc_bid_volume":331.77946138,"highest_52_week_price":0.04167024,"highest_52_week_date":"2019-01-05","lowest_52_week_price":0.01614901,"lowest_52_week_date":"2019-09-06","trade_status":null,"market_state":"ACTIVE","market_state_for_ios":null,"is_trading_suspended":false,"delisting_date":null,"market_warning":"NONE","timestamp":1574673784242,"acc_trade_price_24h":86.0899596010439837,"acc_trade_volume_24h":4209.39183766,"stream_type":"REALTIME"}

If you do not specify whether you want to receive only snapshot information or real-time information, you will receive "Snapshot Information" first and then "Real-time Information" continuously.

If you want to receive information on multiple markets simultaneously, you can indicate multiple markets in the codes field by separating them with commas (,).

For example, if you want to receive only "real-time trade information" in a "simplified format" from the SGD-Bitcoin (SGD-BTC) market and Bitcoin-Ravencoin (BTC-RVN) market, you can make the following request.

$ telsocket -url wss://sg-api.upbit.com/websocket/v1
Connected!
[{"ticket":"test"},{"format":"SIMPLE"},{"type":"trade","codes":["SGD-BTC","BTC-RVN"]}]
{"mk":"SGD-BTC","tms":1523531768829,"td":"2018-04-12","ttm":"11:16:03","ttms":1523531763000,"tp":7691000.0,"tv":0.00996719,"ab":"BID","pcp":7429000.00000000,"c":"RISE","cp":262000.00000000,"sid":1523531768829000,"st":"SNAPSHOT"}
 {"mk":"BTC-RVN","tms":1523531745481,"td":"2018-04-12","ttm":"11:15:48","ttms":1523531748370,"tp":0.09601999,"tv":0.18711789,"ab":"BID","pcp":0.09618000,"c":"FALL","cp":0.00016001,"sid":15235317454810000,"st":"SNAPSHOT"}
 {"mk":"SGD-BTC","tms":1523531769250,"td":"2018-04-12","ttm":"11:16:04","ttms":1523531764000,"tp":7691000.0,"tv":0.07580113,"ab":"BID","pcp":7429000.00000000,"c":"RISE","cp":262000.00000000,"sid":1523531769250000,"st":"REALTIME"}
 ...
$ telsocket -url wss://id-api.upbit.com/websocket/v1
Connected!
> [{"ticket":"test"},{"format":"SIMPLE"},{"type":"trade","codes":["IDR-BTC"]},{"format":"SIMPLE"}]
{"ty":"trade","cd":"IDR-BTC","tms":1574675162100,"td":"2019-11-25","ttm":"09:46:01","ttms":1574675161000,"tp":96670000.0,"tv":0.02958988,"ab":"ASK","pcp":99850000.00000000,"c":"FALL","cp":3180000.00000000,"sid":1574675161000001,"st":"SNAPSHOT"}
{"ty":"trade","cd":"IDR-BTC","tms":1574675342766,"td":"2019-11-25","ttm":"09:49:02","ttms":1574675342000,"tp":97080000.0,"tv":0.01029073,"ab":"BID","pcp":99850000.00000000,"c":"FALL","cp":2770000.00000000,"sid":1574675342000000,"st":"REALTIME"}

In the same way, you will receive a snapshot first, followed by the real-time transaction status.

All of the above requests are based on the assumption that the WebSocket connection is successful.

Some additional request examples are as follows.

  1. trade data of the SGD-BTC and BTC-XRP markets.
    [{"ticket":"UNIQUE_TICKET"},{"type":"trade","codes":["SGD-BTC","BTC-XRP"]}]
  2. orderbook data of the SGD-BTC and BTC-XRP markets
    [{"ticket":"UNIQUE_TICKET"},{"type":"orderbook","codes":["SGD-BTC","BTC-XRP"]}]
  3. trade data from the SGD-BTC market and orderbook data from the BTC-ETH market
    [{"ticket":"UNIQUE_TICKET"},{"type":"trade","codes":["SGD-BTC"]},{"type":"orderbook","codes":["BTC-ETH"]}]
  4. trade data from the SGD-BTC market, orderbook data from the BTC-ETH market, ticker data from the BTC-EOS market
    [{"ticket":"UNIQUE_TICKET"},{"type":"trade","codes":["SGD-BTC"]},{"type":"orderbook","codes":["BTC-ETH"]},{"type":"ticker", "codes":["BTC-EOS"]}]

If you are requesting multiple types of information simultaneously, you can categorize the information types through the "type" field in DEFAULT format and "ty" field in SIMPLE format.