Networking functions

Socket API Reference

Core Functions

Socket Creation

int socket(int family, int type, int protocol);
Creates a socket with the specified parameters:

• family: Address family. Common values:
  • AF_INET (IPv4)
  • AF_INET6 (IPv6)
• type: Socket type. Common values:
  • SOCK_STREAM (TCP)
  • SOCK_DGRAM (UDP)
• protocol: Protocol to use. Common values:
  • IPPROTO_TCP (TCP)
  • IPPROTO_UDP (UDP)

### Socket Closure
```cpp
int close(int socket);

Closes the specified socket.

Network Byte Order Conversion

Functions to convert between host and network byte order:

short htons(short value);  // Host TO Network Short
long htonl(long value);    // Host TO Network Long
short ntohs(short value);  // Network TO Host Short
long ntohl(long value);    // Network TO Host Long

Connection Management

Connect to a Server

int connect(int _socket, const struct sockaddr* server, socklen_t serverlen);

• _socket: Socket to connect.
• server: Structure representing the server to connect to.
• serverlen: Size of the server structure (typically sizeof(server)).

Note

This call is blocking until the connection is established or an error occurs.

Example:

sockaddr_in server;
server.sin_addr.s_addr = inet_addr(const char* ipaddress);
server.sin_family = AF_INET;
server.sin_port = htons(int port);

Data Transmission

int send(int socket, const void* datas, size_t len, int flags);
int recv(int socket, void* buffer, size_t len, int flags);

• socket: Socket for sending/receiving data.
• datas/buffer: Data to send/receive.
• len: Maximum data size in bytes.
• flags: Options mask (usually 0).

Socket Binding

int bind(SOCKET sckt, const struct addr* name, int namelen);

Assigns a local address to a socket:

• sckt: Socket to bind.
• name: Address structure to assign.
• namelen: Size of the structure (use sizeof).

Example:

sockaddr_in addr;
addr.sin_addr.s_addr = INADDR_ANY; // Accept connections from any source
addr.sin_port = htons(port);        // Convert port to network byte order
addr.sin_family = AF_INET;          // TCP socket

Listening for Connections

int listen(SOCKET sckt, int backlog);

• sckt: Server socket to listen on.
• backlog: Maximum number of pending connections. Use SOMAXCONN for system default.

Accepting Connections

SOCKET accept(SOCKET sckt, struct sockaddr* addr, int* addrlen);

Accepts an incoming connection:

• sckt: Server socket waiting for connections.
• addr: Will store the client's address.
• addrlen: Size of the addr structure.

Address Conversion

const char* inet_ntop(int family, const void* src, char* dst, socklen_t size);

Converts a binary IP address (IPv4/IPv6) to a human-readable string:

• family: Address family (AF_INET or AF_INET6).
• src: Pointer to the binary address.
• dst: Buffer to store the readable address.
• size: Maximum buffer size.

Event Monitoring with poll

#include <poll.h>
int poll(struct pollfd *fds, nfds_t nfds, int timeout);

Monitors multiple file descriptors (sockets, files, etc.) for readiness (read/write/error) without blocking. pollfd Structure:

struct pollfd {
    int fd;         // File descriptor to monitor
    short events;   // Events to monitor (INPUT)
    short revents;  // Events that occurred (OUTPUT)
};