WebSocket transport in GraphQL - Step-by-Step Execution

Concept Flow - WebSocket transport

Client initiates WebSocket connection

↓

Server accepts connection

↓

Client sends GraphQL subscription request

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Server processes subscription

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Server sends real-time data updates

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Client receives updates and processes

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Connection stays open for continuous data

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Client or server closes connection

This flow shows how a client and server use WebSocket to keep a live connection for GraphQL subscriptions, sending and receiving real-time data continuously.

Execution Sample

GraphQL

1. Client opens WebSocket to server
2. Client sends subscription query
3. Server acknowledges and starts sending data
4. Server sends data updates as events occur
5. Client receives and processes updates
6. Connection remains open until closed

This sequence shows the steps of establishing and using WebSocket transport for GraphQL subscriptions to get live data updates.

Execution Table

Step	Action	Message Type	Data Sent/Received	Connection State
1	Client opens WebSocket	Connection Request	null	Open
2	Server accepts connection	Connection Ack	null	Open
3	Client sends subscription query	Subscription Start	{"query": "subscription { newMessages }"}	Open
4	Server acknowledges subscription	Subscription Ack	Subscription accepted	Open
5	Server sends data update	Data	{"newMessages": "Hello!"}	Open
6	Client receives data update	Data	{"newMessages": "Hello!"}	Open
7	Server sends another update	Data	{"newMessages": "How are you?"}	Open
8	Client receives second update	Data	{"newMessages": "How are you?"}	Open
9	Client closes connection	Connection Terminate	null	Closed
10	Server acknowledges close	Connection Closed	null	Closed

💡 Connection closed by client at step 9, ending WebSocket session

Variable Tracker

Variable	Start	After Step 3	After Step 5	After Step 7	Final
Connection State	Closed	Open	Open	Open	Closed
Subscription Status	null	Started	Active	Active	Terminated
Received Data	null	null	{"newMessages": "Hello!"}	{"newMessages": "How are you?"}	{"newMessages": "How are you?"}

Key Moments - 3 Insights

Why does the connection stay open after the first data update?

Because WebSocket transport keeps the connection open to continuously send real-time updates, as shown in steps 5 to 8 in the execution_table.

What happens if the client closes the connection?

The connection state changes to Closed, and the server acknowledges this closure, ending the session as seen in steps 9 and 10.

How does the client start receiving live data?

By sending a subscription query (step 3) and receiving an acknowledgment (step 4), the server then sends live data updates (steps 5 and 7).

Visual Quiz - 3 Questions

Look at the execution_table, what is the connection state after step 4?

A Closed

B Open

C Pending

D Terminated

💡 Hint

Check the 'Connection State' column at step 4 in the execution_table.

At which step does the client send the subscription query?

A Step 2

B Step 5

C Step 3

D Step 9

💡 Hint

Look for 'Client sends subscription query' in the Action column of the execution_table.

If the client never closes the connection, what would happen to the connection state in variable_tracker?

A It would remain 'Open' after the final step

B It would change to 'Closed' automatically

C It would become 'Pending'

D It would reset to 'null'

💡 Hint

Refer to the 'Connection State' row in variable_tracker and consider what closing the connection does at step 9.

Concept Snapshot

WebSocket transport keeps a live connection open between client and server.
Client sends a subscription query to start receiving real-time data.
Server sends updates as events happen without reconnecting.
Connection stays open until client or server closes it.
Used mainly for GraphQL subscriptions to get live updates.

Full Transcript

WebSocket transport in GraphQL starts when the client opens a WebSocket connection to the server. The server accepts this connection, and the client sends a subscription query to listen for live data. The server acknowledges the subscription and begins sending data updates as events occur. The client receives these updates continuously while the connection remains open. This live connection allows real-time data flow without repeated requests. Finally, either the client or server can close the connection to end the session. This process enables efficient live data updates in applications.