battleship

A very simple implementation of battleship in C with basic TCP multiplayer and an ncurses interface.

Yes, this is my first C program, and yes, I learned Rust before I learned C. Why? Higher-level APIs. This is more about me learning how to use sockets than something real.

This program also, probably, leaks memory. So make sure you use a kernel that isn't 30 years old.

Compiling

Dependencies

You'll need SDL2 (plus headers), and that's about it. This is because the client uses it to play the TTS voice when something happens.

To compile, you will also need your distro's build-essentials group (or equivalent) which you should have already.

Make

Once you have the dependencies, you should be able to run make, or optionally, make server/make client if you only want to compile the server or client, for whatever reason. This will also download libsam automatically.

Packet Format

Now I'll describe my, mostly pointless, custom packet format.

Header

Header Length: 1 byte.

Each packet will begin with a header, as such:

Field	Size
PACKET_TYPE	1 byte

It's just a single byte that determines what the data portion of the packet will look like. This is handy, since when reading the packet you need only read the first byte to know how much more to read.

0x0 - NONE

Content Length: 0 bytes.

This packet should never be sent, and if it has been sent, then the socket was probably closed without prior notice.

0x1 - LOGIN

Content Length: 16 bytes.

This packet is the first sent by the player, specifying their username in ASCII-only characters.

Field	Size
USERNAME	16 bytes

0x2 - LOGIN_CONFIRM

Content Length: 1 byte.

This packet is sent by the server to the player right after LOGIN, notifying the player of their ID (either 1 or 2 for now).

Field	Size
ID	1 byte

0x3 - SETUP

Content Length: 16 bytes.

This packet is sent to both players by the server when it is ready to recieve ship placements/start setup.

Field	Size
OPPONENT_USERNAME	16 bytes

0x4 - PLACE

Content Length: 10 bytes.

This packet is sent by each player to the server after START. It determines where each player wants to put each ships, determined by their leftmost or uppermost coordinate.

Field	Size
CARRIER	2 bytes
BATTLESHIP	2 bytes
CRUISER	2 bytes
SUBMARINE	2 bytes
DESTROYER	2 bytes

Each ship has the first byte be 0 if it is horizontal and 1 if it is vertical. Then, the next byte is the position. This is identical to the position of SELECT, for instance.

0x5 - TURN

Content Length: 1 byte.

This is sent to both player by the server, informing them of who's turn it is.

Field	Size
PLAYER	1 byte

PLAYER is just the ID of the active player.

0x6 - SELECT

Content Length: 1 byte.

This is sent to the server by a player in order for them to select a tile to strike.

Field	Size
POSITION	1 byte

Here, in POSITION the lower 4 bits determine the x-coordinate (1-10) and the higher four bits the y-coordinate (A-J).

0x7 - TURN_RESULT

Content Length: 3 bytes.

This is sent to both players to notify them whether the previous strike was successful or not, and where it was.

Field	Size
PLAYER	1 byte
POSITION	1 byte
RESULT	1 byte

• PLAYER is the ID of the player who's turn it was.
• POSITION is in the same as in the SELECT packet.
• RESULT can either be 0 for a miss, 1 for a hit, 2 for a sink, and 3 for a win.

0x8 - QUIT

Content Length: 0 bytes.

This can be sent by a player at any time, and will end the game right after it is sent to the server. In this case, the server will then send back the QUIT packet to both clients, indicating that a player quit.

Additionally, if a client sends an invalid packet due to a mistake on the client side, then this packet will also be sent by the server to both players.