--- tags: - The-Ccategories: - Codingdate:# created: 2025-02-26# updated: 2025-02-26---

Socket-first exploration

1. Socket() function### (1). domain protocol family: 1. AF_INET 2. AF_INET6 3. AF_LOCAL(AF_UNIX) 4. AF_ROUTE### (2). Type socket type 1. SOCK_STREAM 2. SOCK_DGRAM 3. SOCK_RAW 4. SOCK_PACKET 5. SOCK_SEQPACKET### (3). Protocol 1. IPPROTO_TCP 2. IPPROTO_UDP 3. IPPROTO_STCP 4. IPPROTO_TIPC## 2. Bind() function```

Int bind(int sockfd, const struct sockaddr *addr, socklen_t addrlen)

- Sockfd: socket descriptor, uniquely identifies a socket- addrlen: address length- addr: an address pointer pointing to the protocol address to be bound to sockfd For example, ipv4 corresponds to: struct sockaddr_in {
sa_family_t sin_family;
in_port_t sin_port;
struct in_addr sin_addr;
};
struct in_addr {
uint32_t s_addr;
};
Corresponding to ipv6 is: struct sockaddr_in6 {
sa_family_t sin6_family;
in_port_t sin6_port;
uint32_t sin6_flowinfo;
struct in6_addr sin6_addr;
uint32_t sin6_scope_id;
};

struct in6_addr {  
unsigned char s6_addr[16];  
};

The Unix domain corresponds to: #define UNIX_PATH_MAX 108
struct sockaddr_un {
sa_family_t sun_family;
char sun_path[UNIX_PATH_MAX];
}; ```

3. Listen() connect() function

Int listen(int sockfd, int backlog)Int connect(int sockfd, const struct sockaddr *addr, socklen_t addrlen)
- The listen function changes the active type created by the socket into a passive type and waits for the client to connect.

4. accept function```

Int socket(int domain, int type, int protocol)

## 5. setsockopt function```
Int setsockopt(SOCKET s, int level, int optname, const char FAR *optval, int optlen)

• s:socket descriptor- Level: option level, SOL_SOCKET/IPPROTO_TCP- Optname: Options that need to be set- optval: just want to store the pointer of the option- Optlen: buffer length

Ref[1]. Netstat-common parameters

[2]. OSI model