How to verify data integrity between client-server connection?

I recently developed an online multiplayer game and it's working fine. There's a central server handling TCP connections with clients, and they both receive and send data. Is there a way to verify that the data sent hasn't been modified before the receiver reads it? Does a TCP connection handle it in some way? If not what is the best way (not asking for code) to implement it? By now I came up with those ideas: - Modify the data sent adding some sort of verify-value, such the packet length. - When a packet is received, ask the server to send it again and verify if they are equal. I searched for a common used solution but couldn't find much. Encryption should be my last option. Edit For a simple way to achieve this: - MD5 - Wikipedia - Example - SHA1 - Wikipedia - Example - SSL - Wikipedia - Example