1. Sockets

2. What is Socket?
The end point of communication between 2 systems on a network (combination of IP&port on each end of the communication)
4-Tuple
Name of API

3. http://inst. eecs. berkeley

4. Socket in C Stream Socket or Connection Oriented Socket
Header files used
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>

5. Socket: Server side
int sockt, newsockt; … sockt = socket(AF_INET, SOCK_STREAM, 0);
Address Family:
AF_INET or AF_UNIX
Socket Type:
SOCK_STREAM or SOCK_DGRAM
Protocol:
0 for appropriate protocol selected by OS

6. If sockt > 0
Socket openning successful

7. struct sockaddr_in s_addr, c_addr; … struct sockaddr_in { short sin_family; u_short sin_port; struct in_addr sin_addr; char sin_zero[8]; }
AF_INET
Not use

8. Initialize sockaddr_in
bzero((char *) &s_addr, sizeof(s_addr)); bzero((char *) &c_addr, sizeof(c_addr));

9. Set sockaddr_in
Must be
s_addr.sin_family = AF_INET; s_addr.sin_port = htons(2048); s_addr.sin_addr.s_addr = INADDR_ANY
Constant or Symbolic link
Represent host’s IP address
Convert to
Networks Byte Order

10. Binding socket
bind(sockt, (struct sockaddr *) &s_addr, sizeof(s_addr));
bind
returns 0 on success
returns -1 in case of fail

11. Waiting for connection
listen(sockt, 5);
Size of backlog queue
Socket to be used for listening

12. Accept a remote connection
int caddr_len = sizeof(c_addr); …
newsockt = accept(sockt, (struct sockaddr *) &c_addr, &caddr_len);
accept() blocks the process
Returns -1 in case of fail
Returns non-negative in case of success

13. Receive data via opened socket
char buffer[256]; int n; …
bzero(buffer, 256);
n = read(newsockt, buffer, 255);
read() blocks the process until there is something to read
read() returns number of bytes read
read() reads 255 bytes or less

14. Send data via opened socket
int n; … n = write(newsockt, “Test 1234”, 9); - write() returns number of sent bytes

15. Close Socket
close(newsockt); close(sockt);

16. Socket: Client side Library Ip address of remote host sys/types.h
sys/socket.h
netinet/in.h
netdb.h or arpa/inet.h
Ip address of remote host
Is known -> inet_pton() is
define in this lib.
Structure hostent and
gethostbyname() function are
defined in this library

17. struct hostent. remoteServ … struct hostent { char. h_name; char
struct hostent *remoteServ … struct hostent { char *h_name; char **h_aliases; int h_addrtype; int h_length; char **h_addr_list; #define h_addr h_addr_list[0] };
Host name
Alias name list
Host address type
Address length
Address list from name server
For backward compatibity

18. Get remote host by name
struct sockaddr_in sock_serv; … remoteServ = gethostbyname(“ bzero((char *) &sock_serv, sizeof(sock_serv)); sock_serv.sin_family = AF_INET; bcopy((char *)remoteServ->h_addr, (char *) &sock_serv.sin_addr.s_addr, remoteServ->h_length); sock_serv.sin_port = htons(2048);

19. gethostbyname() return null if fail

20. IP of remote host is known
inet_pton(int af, char *src, void *dst);
Address family: AF_INET
struct in_addr
Or converted IP
IP address in string form
inet_pton returns 1 on success, returns 0 on failure

21. sock_serv. sin_family = AF_INET; sock_serv
sock_serv.sin_family = AF_INET; sock_serv.sin_port = htons(2048); Inet_pton(AF_INET, “ ”, &sock_serv.sin_addr);

22. Connect to remote host
int sockHandle; … connect(sockHandle, &sock_serv, sizeof(sock_serv));
connect() returns
0 on success
1 on failure

23. Datagram Socket or Connectionless Socket
int dsock; …
dsock = socket(AF_INET, SOCK_DGRAM, 0)

24. Datagram receive data
int n, remoteL; char buf[256]; struct sockaddr_in remoteS; … n = recvfrom(dsock,buf,256,0, &remoteS, &remoteL);

25. Datagram send data
struct sockaddr_in serv; int servL; … n=sendto(dsock, buf, strlen(buf), 0, &serv, servL);

26. Socket in C# Library using System; using System.Net;
using System.Net.Sockets;

27. Create Socket object
Socket newsock = new Socket(AddressFamily.InterNetwork, SocketType.Stream, ProtocolType.Tcp);

28. Binding socket & Listen
Stream Socket
Binding socket & Listen
IPEndPoint ipep = new IPEndPoint(IPAddress.Any, 2048); … newsock.Bind(ipep); newsock.Listen(5);

29. Connect
IPEndPoint ipep = new IPEndPoint( IPAddress.Parse(" "), 2048); … server.Connect(ipep);

30. Accept
Socket client = newsock.Accept();

31. Send & Receive
byte[] data = new byte[1024]; int recv; … string welcome = "Welcome to my test server"; data = Encoding.ASCII.GetBytes(welcome); client.Send(data, data.Length, SocketFlags.None); recv = client.Receive(data);

32. Close socket
client.Shutdown(SocketShutdown.Both); client.Close(); newsock.Shutdown(SocketShutdown.Both); newsock.Close();

33. Datagram Socket
Create Socket object: Socket newsock = new Socket(AddressFamily.InterNetwork, SocketType.Dgram, ProtocolType.Udp);

34. Send data
SendTo(byte[] data, EndPoint Remote) SendTo(byte[] data, SocketFlags Flags, EndPoint Remote) SendTo(byte[] data, int Size, SocketFlags Flags, EndPoint Remote) SendTo(byte[] data, int Offset, int Size, SocketFlags Flags, EndPoint Remote)

35. Example:
byte[] data = new byte[1024]; IPEndPoint ipep = new IPEndPoint( IPAddress.Parse(" "), 9050); … string welcome = "Hello, are you there?"; data = Encoding.ASCII.GetBytes(welcome); server.SendTo(data, data.Length, SocketFlags.None, (Endpoint) ipep);

36. Receive data
ReceiveFrom(byte[] data, ref EndPoint Remote)

37. Example:
int recv; byte[] data = new byte[1024]; IPEndPoint sender = new IPEndPoint(IPAddress.Any, 0); EndPoint Remote = (EndPoint)(sender); … recv = newsock.ReceiveFrom(data, ref Remote);