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POUsage of htonl() and ntonhl() for unsigned char
 

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  1. POUsage of htonl() and ntonhl() for unsigned char
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    <p>I am pasting my client and server code below. My program is running fine, except that i am trying to send an ipaddress in my src and dest field, and for some reason, even though i am sending it as 131.199.166.232, it is printing as 232.166.199.131. But rest of my packet values are printed in a proper way. I have used memcpy(), so I feel its a memcpy thing, which somewhere I did wrong, but in Beej's guide as there is a section @ the byte ordering in different computer architectures.....I have not used htonl() and all, so maybe it is because of that.Please guide me as where I am going wrong. Also kindly tell me the way i am sending data, how should the htonl() function can be used in my code....Thanks in advance.</p> <p>Client: </p> <pre><code> #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;math.h&gt; #include &lt;sys/types.h&gt; #include &lt;sys/socket.h&gt; #include &lt;netinet/in.h&gt; #include &lt;netdb.h&gt; #define MAXPROFILES 2 int main(int argc, char *argv[]) { int sockfd, portno, n; struct sockaddr_in serv_addr; struct hostent *server; unsigned char buf[1024]; unsigned int srcAddress = 2193598184; unsigned int destAddress = 2193598182; struct profile_t { unsigned char length; unsigned char type; unsigned char *data; }; typedef struct profile_datagram_t { unsigned char src[4]; unsigned char dst[4]; unsigned char ver; unsigned char n; struct profile_t profiles[MAXPROFILES]; } header; header outObj; int j =0; int i =0; // for loop for doing the malloc so that we can allocate memory to all profiles for(i=0;i&lt;MAXPROFILES;i++){ outObj.profiles[i].data = malloc(5); } for(i=3;i&gt;=0;i--){ outObj.src[i] = (srcAddress &gt;&gt; (i*8)) &amp; 0xFF; outObj.dst[i] = (destAddress &gt;&gt; (i*8)) &amp; 0xFF; printf("%d",outObj.src[i]); } outObj.ver = 1; outObj.n = 2; memcpy(buf,&amp;outObj.src,4); memcpy(buf+4,&amp;outObj.dst,4); memcpy(buf+8,&amp;outObj.ver,1); memcpy(buf+9,&amp;outObj.n,1); outObj.profiles[0].length = 5; outObj.profiles[0].type = 1; outObj.profiles[1].length = 5; outObj.profiles[1].type = 2; for(i=0;i&lt;MAXPROFILES;i++){ for(j=0;j&lt;5;j++){ outObj.profiles[i].data[j] = j+1; } </code></pre> <p>}</p> <pre><code> int k = 10; // for loop to do memcopy of length,type and data. for(i=0;i&lt;MAXPROFILES;i++){ memcpy(buf+k,&amp;outObj.profiles[0].length,1); memcpy(buf+k+1,&amp;outObj.profiles[0].type,1); memcpy(buf+k+2,outObj.profiles[0].data,5); k +=7; </code></pre> <p>}</p> <pre><code> if (argc &lt; 3) { fprintf(stderr,"usage: %s hostname port\n", argv[0]); exit(0); } portno = atoi(argv[2]); //Convert ASCII to integer sockfd = socket(AF_INET, SOCK_STREAM, 0); // socket file descriptor if (sockfd &lt; 0) error("ERROR DETECTED !!! Problem in opening socket\n"); server = gethostbyname(argv[1]); if (server == NULL) { fprintf(stderr,"ERROR DETECTED !!!, no such server found \n"); exit(0); } bzero((char *) &amp;serv_addr, sizeof(serv_addr)); //clear the memory for server address serv_addr.sin_family = AF_INET; bcopy((char *)server-&gt;h_addr, (char *)&amp;serv_addr.sin_addr.s_addr, server-&gt;h_length); serv_addr.sin_port = htons(portno); printf("Client 1 trying to connect with server host %s on port %d\n", argv[1], portno); if (connect(sockfd,(struct sockaddr *)&amp;serv_addr,sizeof(serv_addr)) &lt; 0) error("ERROR in connection"); printf("SUCCESS !!! Connection established \n"); if (write(sockfd, buf, k) &lt; 0) { error("Write error has occured "); } return 0; </code></pre> <p>Server: </p> <pre><code> #include &lt;stdio.h&gt; #include &lt;stdlib.h&gt; #include &lt;string.h&gt; #include &lt;sys/types.h&gt; #include &lt;sys/socket.h&gt; #include &lt;netinet/in.h&gt; #define MAXPROFILES 2 int main(int argc, char *argv[]) { int sockfd, newsockfd, portno, clilen; struct sockaddr_in serv_addr, cli_addr; unsigned char buf[1024]; int my_data2[10] = {1,3,9,10}; int my_data[10] = {1,2,3,4,5}; int myDataBinary[500] = {0}; int myDataBinary2[500] = {0}; int recData[500] = {0}; int index1=0; struct profile_t { unsigned char length; unsigned char type; unsigned char *data; }; typedef struct profile_datagram_t { unsigned char src[4]; unsigned char dst[4]; unsigned char ver; unsigned char n; struct profile_t profiles[MAXPROFILES]; } header; header outObj; int j =0; int i =0; if (argc &lt; 2) { fprintf(stderr,"usage: %s port_number1",argv[0]); exit(1); } sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd &lt; 0) error("ERROR DETECTED !!! Problem in opening socket"); bzero((char *) &amp;serv_addr, sizeof(serv_addr)); portno = atoi(argv[1]); serv_addr.sin_family = AF_INET; serv_addr.sin_addr.s_addr = htonl(INADDR_ANY); serv_addr.sin_port = htons(portno); if (bind(sockfd, (struct sockaddr *) &amp;serv_addr, sizeof(serv_addr)) &lt; 0) error("ERROR DETECTED !!! There was a problem in binding"); listen(sockfd, 10); clilen = sizeof(cli_addr); printf("Server listening on port number %d...\n", serv_addr.sin_port); newsockfd = accept(sockfd,(struct sockaddr *) &amp;cli_addr, &amp;clilen); if (newsockfd &lt; 0) error("ERROR DETECTED !!! the connection request was not accepted"); int rc = read(newsockfd,buf,100); if(rc &lt; 0){ printf("error"); } else { printf("success %d",rc); } memcpy(&amp;outObj.src,buf+0,4); memcpy(&amp;outObj.dst,buf+4,4); memcpy(&amp;outObj.ver,buf+8,1); memcpy(&amp;outObj.n,buf+9,1); printf("\nsrc ip = "); for(int i=0;i&lt;4;i++){ printf("%d ",outObj.src[i]); } printf("\ndest ip = "); for(int i=0;i&lt;4;i++){ printf("%d ",outObj.src[i]); } printf("\nversion = %d",outObj.ver); printf("\nnumber = %d",outObj.n); int k = 10; for(i=0;i&lt;outObj.n;i++){ memcpy(&amp;outObj.profiles[i].length,buf+k,1); memcpy(&amp;outObj.profiles[i].type,buf+k+1,1); outObj.profiles[i].data = malloc(outObj.profiles[i].length); memcpy(outObj.profiles[i].data,buf+k+2,5); k +=7; } for(int i=0;i&lt;outObj.n;i++){ printf("\nMessage %d :",i+1); printf("\nLength : %d",outObj.profiles[i].length); printf("\nType : %d",outObj.profiles[i].type); for(int j=0;j&lt;5;j++){ printf("\ndata %d : %d",j,outObj.profiles[i].data[j]); } } for(int i=0; i&lt;sizeof(my_data)/sizeof(int);i++) { if(my_data[i] &gt; 0){ index1 = my_data[i]; myDataBinary[index1] = 1; printf("my data %d = %d\n",index1,myDataBinary[index1]); } } for(int i=0; i&lt;sizeof(my_data2)/sizeof(int);i++) { if(my_data2[i] &gt; 0){ index1 = my_data2[i]; myDataBinary2[index1] = 1; printf("my data %d = %d\n",index1,myDataBinary2[index1]); } } int sumRecievedData = 0; int sumMyData = 0; int sumMultpliedData = 0; float Cov =0; float sdMyData = 0; float sdRecievedData =0; int n = 500; float rho; for(int i=0;i&lt;outObj.n;i++){ index1=0; for (int j=0; j&lt;outObj.profiles[i].length;j++) { if(outObj.profiles[i].data[j] &gt; 0){ index1 = outObj.profiles[i].data[j]; recData[index1] = 1; printf("rec data %d = %d\n",index1,recData[index1]); } } } return 0; } </code></pre>
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    1. USuser537670
    1. USuser537670
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    1. CO`htnol` is designed to work on `long int` values. What do you expect it to do with a `char *`?
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      1. USOliver Charlesworth
    2. CO@Oli: http://stackoverflow.com/questions/6863216/error-in-socket-programming-and-use-of-htonl-htons-functions-in-c/6864860#6864860.....this is the link which has my code and question.
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      1. USuser537670
    3. CObasically i want to do byte-byte ordering for sending and receiving data. i have a unsigned char buf, which I am using to send data and recv data
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      1. POUsage of htonl() and ntonhl() for unsigned char
      1. USuser537670
 

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