WebSocket is designed to provide a full-duplex communication channel over a single TCP connection. As it is built upon TCP, it inherits key characteristics of TCP, including the guarantee of data transmission order.
In the TCP/IP protocol, data packets are received in the order they are sent. If a data packet is lost or corrupted during transmission, TCP will retransmit the lost packet and ensure all packets arrive in the correct sequence at the receiver. Consequently, messages sent via WebSocket will be received in the order they were sent.
For example, if you send three messages via WebSocket: 'Hello', 'How are you?', 'Goodbye', the receiver should receive them in the sequence 'Hello' -> 'How are you?' -> 'Goodbye' regardless of network conditions. If the 'How are you?' message is lost during transmission, TCP will retransmit it and pause the transmission of subsequent messages (such as 'Goodbye') until 'How are you?' is correctly received.
Therefore, applications using WebSocket can depend on message ordering, which is essential for applications that require data sequence integrity, such as real-time chat applications.