send.c

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#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <netdb.h>
#include <unistd.h>
#include <errno.h>
#include <netinet/if_ether.h>
#include <net/if.h>
#include <linux/sockios.h>

typedef unsigned char uint8_t;
typedef unsigned short uint16_t;
typedef unsigned int    uint32_t;

//#define TCP_PORT 31416
#ifndef TCP_PORT
#error Please define TCP_PORT
#endif

int escape(char *message, int size)
{
    char *buffer;
    char *bptr;
    char *mptr;
    int len;
    unsigned char c;

    len = strlen(message);
    if(len > size)
    {
        fprintf(stderr,"message too long\n");
        len = size;
    }

    mptr = message;
    buffer = calloc(len+2,1);
    bptr = buffer;
    if(!buffer)
    {
        perror("Can not allocate buffer\n");
        exit(1);
    }

    while(*mptr)
    {
        c = *mptr++;
        if(c == '\\')
        {
            if(*mptr)
            {
                c = *mptr;
                if( c == 'n')
                {
                    c = '\n';
                    mptr++;
                }
                else if( c == 'r')
                {
                    c = '\r';
                    mptr++;
                }
                else if( c == 't')
                {
                    c = '\t';
                    mptr++;
                }
                else if( c == 'f')
                {
                    c = '\f';
                    mptr++;
                }
            }
        }
        *bptr++ = c;
    }
    *bptr = 0;
    strcpy(message,buffer);
    return(strlen(message));
}

void send_message(char *message, char *ip, int port, int echoback)
{
    int sockfd, portno, n;
    char buffer[4096];

    struct sockaddr_in dest_addr;
    struct hostent *server;

    portno = port;
    // IF UDP use: AF_INET, SOCK_DGRAM, IPPROTO_UDP

    // TCP socket
    sockfd = socket(AF_INET, SOCK_STREAM, IPPROTO_TCP);
    if (sockfd < 0) 
    {
        perror("ERROR opening socket");
        exit(1);
    }

    server = gethostbyname(ip);
    if (server == NULL) {
        fprintf(stderr,"ERROR, no such host\n");
        exit(0);
    }
    printf("Host name: %s\n", server->h_name);

    bzero((char *) &dest_addr, sizeof(dest_addr));
    dest_addr.sin_family = AF_INET;
    bcopy((char *)server->h_addr, 
         (char *)&dest_addr.sin_addr.s_addr,
         server->h_length);
    dest_addr.sin_port = htons(portno);
    if (connect(sockfd,(struct sockaddr *)&dest_addr,sizeof(dest_addr)) < 0) 
    {
        perror("ERROR connecting");
        exit(1);
    }
    n = write(sockfd,message,strlen(message)+1);
    if (n < 0) 
    {
        perror("ERROR writing to socket");
        exit(1);
    }
    
    // reads characters coming back from the connection - debugging
    // interrup to exit
    // this code blocks waiting for input
    if(echoback)
    {
        do
        {
            n = read(sockfd,buffer,sizeof(buffer)-1);
            write(1, buffer, n);
        }
        while(n);
    }

    close(sockfd);
}


int main(int argc,char *argv[])
{
    int i,ret;
    int echoback = 0;
    struct net *p;
    char message[8192];
    char ip[INET_ADDRSTRLEN];
    int port_no = TCP_PORT;

// htonl() and htons()..

    memset(ip,0,sizeof(ip)-1);
    memset(message,0,sizeof(message)-1);
    for(i=1;i<argc;++i) {
        if(strcmp(argv[i],"-i") == 0) {
            strcpy(ip, argv[++i]);
        }
        if(strcmp(argv[i],"-m") == 0) {
            strncpy(message,argv[++i], sizeof(message)-1);
        }
        if(strcmp(argv[i],"-p") == 0) {
            sscanf(argv[++i], "%d", &port_no);
        }
        if(strcmp(argv[i],"-e") == 0) {
            echoback = 1;
        }
    }
        
    if(!strlen(ip) || !strlen(message))
    {
        fprintf(stderr,"usage: -i ip_address -m \"message\" [ -p port ]\n ");
        exit(1);
    }
    if(!strlen(message))
    {
        fprintf(stderr,"Message missing\n");
        exit(1);
    }
    escape(message, sizeof(message)-1);
    printf("ip:%s, port:%d, message:\n%s\n",ip,port_no,message);
    fflush(stdout);
    send_message(message, ip, port_no, echoback);
    return(0);
}