Socket programming in C
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This document discusses socket programming in C. It begins with an introduction to sockets, describing them as an interface between applications and networks that allows processes to communicate. It then covers the client-server model and types of sockets like stream and datagram. The main socket APIs are explained, including functions for creating, binding, listening, connecting, sending, receiving and closing sockets. Examples of socket programming with UDP and TCP are provided, showing the typical functions used in each case. The document concludes by noting that files can also be sent over sockets and models for handling multiple clients like process, thread and worker pools.
Socket programming in C
- 1. Socket Programming in C connecting processes Dipak Kumar Swain MCA 4th Semester Regd No-1105227024
- 2. Overview • Introduction to Sockets • A generic Client-Server application • Types of Socket • Socket APIs • Socket Programming with TCP • Socket Programming with UDP • Conclusion • References 2/11
- 3. Introduction to Sockets What is a Sockets? • Socket is an interface between application and network which is used for communication between processes • Data can be sent to or received through a socket from another process running on the same machine or a different machine • Socket internally represents the three things: – Protocol – IP address – Port number 3/11
- 4. Client Server Application Most interprocess communication uses client-server model • • • Server waits for client to request a connection and Client contacts server to establish a connection. Client sends request and Server sends reply. Client and/or server terminate connection. 4/11
- 5. Client Server Application • What makes a connection? {Source<IP address, Port #> , Destination <IP address, Port #>} i.e. source socket – destination socket pair uniquely identifies a connection. • Example 1343 Client 192.168.0.2 Server 80 1343 Client 192.168.0.3 192.168.0.1 5488 Client 192.168.0.2 5/11
- 6. Types of Socket Two essential types of sockets : – STREAM Socket – Treat communications as a continuous stream of characters. – DATAGRAM Socket– Read entire messages at once. Stream Socket(SOCK_TCP) Datagram Socket(SOCK_DGRAM) TCP UDP Connection Oriented Connection Less Reliable Delivery Unreliable Delivery In-Order Guaranteed No-Order Guaranteed Bidirectional Can Send Or Receive 6/11
- 7. Socket APIs Socket System Call – create an end Socket System Call UDP Socketend Some Essential System calls used byCall –Bind createaddress TCP & – an IP an Bind Systemfor communication Bind System Call –Bind an IP address point socket for communication point socket Listen System Call:– Used by Server Listen System Call:– Used by • socket ( ): and port number with a socket Server and port<sys/socket.h> socket number with a #includein TCP for passively waiting #includeSystem for passively waiting <sys/socket.h> Connect in TCP Call – Initiates a Connect Process System Call – Initiates a Process #include <sys/socket.h> #include <sys/socket.h> • bind( ): Accept SystemTCPSocket. a Accept SystemCall:– Accept a connection on TCP Socket. type, int connection on domain, int for connection domain, int type, int for connection Call:– Accept int socket(intCall– Send data to int socket(int Send Systemsockfd, Send data to Send SystemCallclient connection from client socket. connection from – struct int bind(<sys/socket.h>socket. int int bind(<sys/socket.h> • listen( ): #includeTCP socket. Receive data from #includeTCP sockfd, struct protocol);intsocket.Receive data from protocol); Call – Recv System Call – Recv System another <sys/socket.h> addrlen); another *serv_addr, int sockaddr<sys/socket.h> addrlen); #includeSystemCall – Send datagram sockaddr *serv_addr,Send int #include Sendto System Call integer datagram Sendto TCPunsigned –intstruct another an unsigned integercalled another <sys/socket.h> backlog); int listen( intintsockfd, struct • connect( ): intconnect( int sockfd, listen( intsockfd, sockfd, Returns TCPsocket. intbacklog); connect(socket. Returns <sys/socket.h> #include anSystemCallstructcalled #include System Call– Receive Recvfromonintsockfd, struct Recvfrom*addr, intthe specified UDP socket. to the specified sockfd, – Receive intaccept(*addr, intsocket. to accept(int UDP addrlen); #include0<sys/socket.h> Returnsdescriptorint addrlen); #include on Call sockaddr<sys/socket.h> the Returns 0on success socketSystemsockfd,Closes*msg, int sockaddr int success void socketdescriptor – void the Returns 0 int success *addrlen); int Close Systemsockfd,Closes*msg, • accept( ): int send( packet from*addrlen); int Returns 0 packet from void *msg, Close int send( on success void *msg, datagram *addr, int another UDP int datagram *addr, int sockaddrintintCall – void *msg, int sockaddr sockfd, int sendto( intsockfd, another UDP int sendto( sockfd, int recv( intsockfd, void *msg, int int recv( on success communication channel between size, int 0 on flags, between communication Returns flag);success struct sockaddr size, int 0 int Returns socket flag); flags, struct sockaddr socket a non-negative descriptor • send( ): noOfbytes, int channeldescriptoron noOfbytes, Returns server. size, int flag); Returns server. size, int flag); client & numbersockfd,void *msg,senton client & a non-negative *msg,int on Returns*sock_length); Returns number of characters int int recvfrom( int sockfd, void int int *to,recvfrom( int of characters sent on *to, int success *sock_length); success • recv( ): Returns number of characters sent on Returns int flags,struct sockaddr *from, noOfbytes,number of characters sent on int close(intflags,of bytes written*from, noOfbytes, int close(intsockfd); sockfd); success number of bytes writtento success number struct Returnsorint on error sockaddr to Returnsor-1 on error success int *sock_length); success -1 int *sock_length); • sendto( ): Returnonon success & sockfd is the Returnonsuccess or & on error socket 0 on success -1 sockfd is the socket 0 success or -1 on error Returnsdescriptorofbyteswill befrom Returnsnumber which read from socket descriptorofwhich will be socket number bytes read • recvfrom( ): socket on success or -1 on error socket closed. on success or -1 on error closed. • close( ): 7/11
- 8. Socket Programming With UDP Client Server socket socket bind sendto recvfrom Request Response recvfrom sendto close 8/11
- 9. Socket Programming With TCP Client Server socket socket bind listen connect Connect 3-way handshake accept send/recv recv/send close close 9/11
- 10. Conclusion Not only message can send but also a file can send through Socket. To handle multiple client simultaneously , we can use the following models at server side: Process Model Thread Model Worker Pool Model 10/11
- 11. References • Cystem Programming at the Roots… By Susant K Rout and T Prabakaran • UNIX Network Programming, by Richard Stevens. • LINUX man page Accessible through following command – man 2 <system_call_name> – E.g. man 2 socket 11/11