socket.h

#ifndef _SOCKET_H_
#define _SOCKET_H_

#ifndef SERVER_PORT
    #define SERVER_PORT 30000
#endif

#ifndef MAX_CONNECTIONS
    #define MAX_CONNECTIONS 12
#endif

#ifndef MAX_BACKLOG
    #define MAX_BACKLOG 5
#endif

#ifndef MAX_NAME
    #define MAX_NAME 10
#endif

#ifndef MAX_USER_MSG
    #define MAX_USER_MSG 128
#endif

#ifndef MAX_IMG_LEN
    #define MAX_IMG_LEN 65535
#endif

/*
 * Under our chat protocol, the maximum size of a message sent by a server is:
 * CODE + MAX(username) + SPACE + MAX(user message or image) + CRLF
 */
#ifndef MAX_PROTO_MSG
    #define MAX_PROTO_MSG 1+MAX_NAME+1+MAX_IMG_LEN+2
#endif

/* Working with string functions to parse/manipulate the contents of
 * the buffer can be convenient. Since we are using a text-based
 * protocol (i.e., message contents will consist only of valid ASCII
 * characters) let's leave 1 extra byte to add a NULL terminator
 * so that we can more easily use string functions. We will never
 * actually send a NULL terminator over the socket though.
 */
#ifndef BUF_SIZE
    #define BUF_SIZE MAX_PROTO_MSG+1 
#endif

struct listen_sock {
    struct sockaddr_in *addr;
    int sock_fd;
};

/*
 * Initialize a server address associated with the required port.
 * Create and setup a socket for a server to listen on.
 */
void setup_server_socket(struct listen_sock *s);

/*
 * Search the first n characters of buf for a network newline (\r\n).
 * Return one plus the index of the '\n' of the first network newline,
 * or -1 if no network newline is found.
 * Definitely do not use strchr or other string functions to search here. (Why not?)
 */
int find_network_newline(const char *buf, int n);

/* 
 * Reads from socket sock_fd into buffer *buf containing *inbuf bytes
 * of data. Updates *inbuf after reading from socket.
 *
 * Return -1 if read error or maximum message size is exceeded.
 * Return 0 upon receipt of CRLF-terminated message.
 * Return 1 if socket has been closed.
 * Return 2 upon receipt of partial (non-CRLF-terminated) message.
 */
int read_from_socket(int sock_fd, char *buf, int *inbuf);

/*
 * Search src for a network newline, and copy complete message
 * into a newly-allocated NULL-terminated string **dst.
 * Remove the complete message from the *src buffer by moving
 * the remaining content of the buffer to the front.
 *
 * Return 0 on success, 1 on error.
 */
int get_message(char **dst, char *src, int *inbuf);

/*
 * Write a string to a socket.
 *
 * Return 0 on success.
 * Return 1 on error.
 * Return 2 on disconnect.
 * 
 * See Robert Love Linux System Programming 2e p. 37 for relevant details
 */
int write_to_socket(int sock_fd, char *buf, int len);
 
#endif /* SOCKET_H */