1. Basic Socket Programming TCP/IP overview. TCP interface Reference: –UNIX Network Programming, by Richard Stevens. –UNIX man page.

2. Overview of TCP/IP protocols –Application layer(ssh,http,etc) –Transport layer (TCP, UDP) –Network layer (IPv4, IPv6) –Host to Network layer (Ethernet)

3. Some concepts: –Entity (process/hardware/system calls) –Protocol: How peer entities interact with each other. –Service interface: How upper layer entities interact with lower layer entities.

4. Socket Programming: the use of TCP and UDP. TCP: Transmission control protocol. connection-oriented, reliable, full duplex, byte stream service Interface: socket, bind, listen, accept, connect, read, write, close.

5. –An analogy: Socket: telephone Bind: assign telephone number to a telephone Listen: turn on the ringer so that you can hear the phone call Connect: dial a phone number Accept: answer the phone Read/write: talking Close: ???

6. To send: –Socket, connect write To receive: –Socket, bind, listen, accept read TCP endpoint: –IP address + port number

7. Basic TCP sockets. #include int socket(int family, int type, int protocol); Family: AF_INET (PF_INET). Type: SOCK_STREAM (TCP) SOCK_DGRAM (UDP) Protocol: = 0 Return descriptor, -1 on error.

8. Connect: #include int connect(int sockfd, const struct sockaddr *servaddr, socklen_t addrlen); Servaddr: socket address structure (ip address and port)

9. Socket Address structure: struct in_addr { in_addr_t s_addr; } struct sockaddr_in { uint8_t sin_len; sa_family_t sin_family; in_port_t sin_port; struct in_addr sin_addr; char sin_zero[8]; } Always use sockaddr_in type for manipulation and convert it to sockaddr. See example1.c. struct sockaddr { uint8_t sa_len; sa_family_t sa_family; char sa_data[14]; }

10. Bind –Client does not have to bind, system assigns a dynamic port number. #include int bind(int sockfd, const struct sockaddr &myaddr, socklen_t addlen);

11. Myaddr: (address, port) = (INADDR_ANY, 0) system assigns addr and port. = (INADDR_ANY, !0) system selects addr, user selects port =(Local IP address, 0) user selects addr, system selects port =(Local IP address,!0) user selects both addr and port See example2.c

12. Listen –Convert a socket into a passive socket #include int listen(int sockfd, int backlog) Backlog: number of connections that the kernel should queue for the socket.

13. Accept: Blocking by default #include int accept (int sockfd, struct sockaddr *cliaddr, socklen_t *addrlen); Return client’s address in cliaddr See example2.c

14. What happen when we run example2.c as server on diablo and example1.c as client on linprog? –Sockaddr_in revisit sin_port and sin_addr must be in network byte order. –Check example3.c, what is the difference between diablo and quake?

15. Some useful functions to convert the byte orders #include uint16_t htons(uint16_t host16bitvalue); uint32_t htonl(uint32_t host32bitvalue); uint16_t ntohs(uint16_t net16bitvalue); Uint32_t ntohl(uint32_t net32bitvalue); –See example3.c

16. Some byte manipulation functions : #include Void *memset(void *dst, int c, size_t len); Void *memcpy(void *dst, void *src, size_t nbytes); Void *memcmp(const void *ptr1, const void *ptr2, size_t nbytes); Address conversion functions inet_aton/inet_addr/inet_ntoa