What client information is transmitted to the server during the connection establishment process?

When establishing a connection (for example, a TCP connection), the client transmits the following information to the server:

• Client IP address — for identifying the source of the request.
• Client port — used for routing responses back to the client.
• In the case of higher-level protocols (e.g., HTTP), the client may transmit additional data such as request headers, cookies, User-Agent, etc.

At the TCP/IP level, the main information is the IP address and port of the client, which are necessary for establishing and maintaining the connection.

Example: when establishing a TCP connection, the client initiates a three-way handshake (SYN, SYN-ACK, ACK), during which the server learns the client's IP and port.