socket cheatsheet

socket_cheatsheet.txt

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                                                           '-_____-' '--_______--' '-_____-'-.__________.'          '-__________.'                                                                          
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                                        1. Interaction                                                                                                                                                      
                                                              2. Port and Service Functions                                                                                                                 
                                           TCP Server         getservbyname(char *name, char *proto)  // Fetch port by service name and protocol                                                            
                                      ┌───────────────────┐   getservbyport(int port, char *proto)    // Fetch service name by port and protocol                                                            
                                      │      socket()     │                                                                                                                                                 
                                      └─────────┬─────────┘   3. Byte Ordering Functions                                                                                                                    
                                                │             htons (unsigned short hostshort)  // Convert 16-bit host to network byte order                                                                
                                      ┌─────────▼─────────┐   htonl (unsigned long hostlong)    // Convert 32-bit host to network byte order                                                                
                           known port │       bind()      │   ntohs (unsigned short netshort)   // Convert 16-bit network to host byte order                                                                
                                      └─────────┬─────────┘   ntohl (unsigned long netlong)     // Convert 32-bit network to host byte order                                                                
                                                │                                                                                                                                                           
                                      ┌─────────▼─────────┐   4. IP Address Functions                                                                                                                       
                                      │      listen()     │   inet_aton (const char *strptr, s ruct in_addr *addrptr)  // Convert string to network address                                                 
                                      └─────────┬─────────┘   inet_addr (const char *strptr)  // Convert string to IPv4 address (32-bit network order)                                                      
                                                │             inet_ntoa (struct in_addr inaddr)  // Convert IPv4 address to string                                                                          
                                      ┌─────────▼─────────┐                                                                                                                                                 
                                      │      accept()     │   5. Socket Core Functions                                                                                                                      
                                      └─────────┬─────────┘   socket (int family, int type, int protocol)  // Get socket descriptor                                                                         
                                                │             connect (int sockfd, struct sockaddr *serv_addr, int addrlen)  // Connect to server                                                           
           TCP Client                           ▼             bind (int sockfd, struct sockaddr *my_addr, int addrlen)  // Bind socket to local address                                                     
      ┌───────────────────┐           blocks until connection listen (int sockfd, int backlog)  // Listen for incoming connections                                                                          
      │      socket()     │                from client        accept (int sockfd, struct sockaddr *cliaddr, socklen_t *addrlen)  // Accept connection                                                       
      └─────────┬─────────┘                     │             send (int sockfd, const void *msg, int len, int flags)  // Send data                                                                          
                │                               │             recv (int sockfd, void *buf, int len, unsigned int flags)  // Receive data                                                                    
      ┌─────────▼─────────┐     connection      │             sendto (int sockfd, const void *msg, int len, unsigned int flags, const struct sockaddr *to, int tolen)  // Send to UNCONNECTED socket        
      │     connect()     ◄─────────────────────►             recvfrom (int sockfd, void *buf, int len, unsigned int flags, struct sockaddr *from, int *fromlen)  // Receive from UNCONNECTED socket        
      └─────────┬─────────┘(TCP 3-way handshake)│             close (int sockfd)  // Close socket                                                                                                           
                │                               │             shutdown (int sockfd, int how)  // Gracefully close socket                                                                                    
      ┌─────────▼─────────┐                     │             select (int nfds, fd_set *readfds, fd_set *writefds, fd_set *errorfds, struct timeval *timeout)  // Monitor multiple sockets                  
┌─────►       write()     ┼────┐      ┌─────────▼─────────┐                                                                                                                                                 
│     └─────────┬─────────┘    └──────►      read()       │   6. Socket Helper Functions                                                                                                                    
│               │                     └─────────┬─────────┘   write (int fildes, const void *buf, int nbyte)  // Write to file descriptor                                                                   
│               │                               │             read (int fildes, const void *buf, int nbyte)  // Read from file descriptor                                                                   
│               │                               ▼             fork (void)  // Create new process                                                                                                            
│               │                        process request      bzero (void *s, int nbyte)  // Set memory to 0                                                                                                
│               │                               │             bcmp (const void *s1, const void *s2, int nbyte)  // Compare byte strings                                                                     
│               │                               │             bcopy (const void *s1, void *s2, int nbyte)  // Copy byte strings                                                                             
│               │                     ┌─────────▼─────────┐   memset (void *s, int c, int nbyte)  // Set memory to specific value                                                                           
│               │              ┌──────┼      write()      │                                                                                                                                                 
│    ┌──────────▼────────┐ data(reply)└─────────┬─────────┘   7. Linux Socket Structures                                                                                                                    
└────│       read()      ◄─────┘                │             sockaddr                                                                                                                                      
     └──────────┬────────┘                      │             struct sockaddr { unsigned short sa_family; char sa_data[14]; }  // Generic socket address                                                    
                │                     ┌─────────▼─────────┐   sockaddr_in                                                                                                                                   
                │                     │       read()      │   struct sockaddr_in { short int sin_family; unsigned short int sin_port; struct in_addr sin_addr; unsigned char sin_zero[8]; }  // IPv4 address
                │                     └─────────┬─────────┘   in_addr                                                                                                                                       
     ┌──────────▼────────┐                      │             struct in_addr { unsigned long s_addr; }  // 32-bit IPv4 address                                                                              
     │       close()     ├────┐                 │             hostent                                                                                                                                       
     └───────────────────┘   EOF      ┌─────────▼─────────┐   struct hostent { char *h_name; char **h_aliases; int h_addrtype; int h_length; char **h_addr_list; }  // Host information                     
                              └───────►      close()      │   servent                                                                                                                                       
                                      └───────────────────┘   struct servent { char *s_name; char **s_aliases; int s_port; char *s_proto; }  // Service and port information