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⟩ Socket Programming in C using TCP with Code?

To compile :

* linux : gcc -Wall -o foo foo.c

* solaris :gcc -Wall -o foo foo.c -lsocket -lnsl

1. TCP

* TCP server : simple TCP server

that prints received messages.

source : tcpServer.c

usage : ./tcpServer

* TCP client : simple TCP client

that sends data to server.

source : tcpClient.c

usage :./tcpClient server data1...dataN

/*********** tcpserver.c **********/

by : prasad

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <netdb.h>

#include <stdio.h>

#include <unistd.h>/*close*/

#define SUCCESS 0

#define ERROR 1

#define END_LINE 0x0

#define SERVER_PORT 1500

#define MAX_MSG 100

/* function readline */

int read_line();

int main (int argc, char *argv[])

{

int sd, newSd, cliLen;

struct sockaddr_in cliAddr, servAddr;

char line[MAX_MSG];

/* create socket */

sd = socket(AF_INET, SOCK_STREAM, 0);

if(sd<0) {

perror("cannot open socket ");

return ERROR;

}

/* bind server port */

servAddr.sin_family = AF_INET;

servAddr.sin_addr.s_addr = htonl(INADDR_ANY);

servAddr.sin_port = htons(SERVER_PORT);

if(bind(sd, (struct sockaddr *) &servAddr,

sizeof(servAddr))<0) {

perror("cannot bind port ");

return ERROR;

}

listen(sd,5);

while(1) {

printf("%s: waiting for data on port TCP %un"

,argv[0],SERVER_PORT);

cliLen = sizeof(cliAddr);

newSd = accept(sd, (struct sockaddr *)

&cliAddr, &cliLen);

if(newSd<0) {

perror("cannot accept connection ");

return ERROR;

}

/* init line */

memset(line,0x0,MAX_MSG);

/* receive segments */

while(read_line(newSd,line)!=ERROR) {

printf("%s: received from %s:TCP%d :

%sn", argv[0],

inet_ntoa(cliAddr.sin_addr),

ntohs(cliAddr.sin_port), line);

/* init line */

memset(line,0x0,MAX_MSG);

} /* while(read_line) */

} /* while (1) */

}

/* WARNING WARNING WARNING WARNING WARNING

WARNING WARNING */

/* this function is experimental..

I don't know yet if it works */

/* correctly or not. Use Steven's

readline() function to have */

/* something robust. */

/* WARNING WARNING WARNING

WARNING WARNING WARNING WARNING */

/* rcv_line is my function readline().

Data is read from the socket when */

/* needed, but not byte after bytes.

All the received data is read.

*/

/* This means only one call to recv(),

instead of one call for

*/

/* each received byte.

*/

/* You can set END_CHAR to whatever

means endofline for you. (0x0A is n)*/

/* read_lin returns the number of

bytes returned in line_to_return

*/

int read_line(int newSd, char *line_to_return)

{

static int rcv_ptr=0;

static char rcv_msg[MAX_MSG];

static int n;

int offset;

offset=0;

while(1) {

if(rcv_ptr==0) {

/* read data from socket */

memset(rcv_msg,0x0,MAX_MSG);

/* init buffer */

n = recv(newSd, rcv_msg, MAX_MSG, 0);

/* wait for data */

if (n<0) {

perror(" cannot receive data ");

return ERROR;

} else if (n==0) {

printf(" connection closed by clientn");

close(newSd);

return ERROR;

}

}

/* if new data read on socket */

/* OR */

/* if another line is still in buffer */

/* copy line into 'line_to_return' */

while(*(rcv_msg+rcv_ptr)!=

END_LINE && rcv_ptr<n) {

memcpy(line_to_return+offset,rcv_msg+rcv_ptr,1);

offset++;

rcv_ptr++;

}

/*end of line + end of buffer =<returnline*/

if(rcv_ptr==n-1) {

/* set last byte to END_LINE */

*(line_to_return+offset)=END_LINE;

rcv_ptr=0;

return ++offset;

}

/* end of line but still some data in

buffer =>return line */

if(rcv_ptr <n-1) {

/* set last byte to END_LINE */

*(line_to_return+offset)=END_LINE;

rcv_ptr++;

return ++offset;

}

/* end of buffer but line is not ended =>*/

/* wait for more data to arrive on socket */

if(rcv_ptr == n) {

rcv_ptr = 0;

}

} /* while */

}

/******* tcpclient.c *******/

/* tcpClient.c */

#include <sys/types.h>

#include <sys/socket.h>

#include <netinet/in.h>

#include <arpa/inet.h>

#include <netdb.h>

#include <stdio.h>

#include <unistd.h> /*close*/

#define SERVER_PORT 1500

#define MAX_MSG 100

int main (int argc, char *argv[]) {

int sd, rc, i;

struct sockaddr_in localAddr, servAddr;

struct hostent *h;

if(argc < 3) {

printf("usage: %s <server> <data1>

<data2> ... <dataN>n",argv[0]);

exit(1);

}

h = gethostbyname(argv[1]);

if(h==NULL) {

printf("%s: unknown host '%s'n"

,argv[0],argv[1]);

exit(1);

}

servAddr.sin_family = h-<h_addrtype;

memcpy((char *) &servAddr.sin_addr.s_addr,

h-<h_addr_list[0],h-<h_length);

servAddr.sin_port = htons(SERVER_PORT);

/* create socket */

sd = socket(AF_INET, SOCK_STREAM, 0);

if(sd<0) {

perror("cannot open socket ");

exit(1);

}

/* bind any port number */

localAddr.sin_family = AF_INET;

localAddr.sin_addr.s_addr =

htonl(INADDR_ANY);

localAddr.sin_port = htons(0);

rc = bind(sd, (struct sockaddr *) &

localAddr, sizeof(localAddr));

if(rc<0) {

printf("%s: cannot bind port TCP %un",

argv[0],SERVER_PORT);

perror("error ");

exit(1);

}

/* connect to server */

rc = connect(sd, (struct sockaddr *)

&servAddr, sizeof(servAddr));

if(rc<0) {

perror("cannot connect ");

exit(1);

}

for(i=2;i<argc;i++) {

rc = send(sd, argv[i], strlen(argv[i])

+ 1, 0);

if(rc<0) {

perror("cannot send data ");

close(sd);

exit(1);

}

printf("%s: data%u sent (%s)n",

argv[0],i-1,argv[i]);

}

return 0;

}

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