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POAccessing buffer using read() in sockets
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copied!<p>In my socket code I have the following structure:</p> <p>Server:</p> <pre><code> #include <stdio.h> #include <stdlib.h> #include <string.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #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]; char* pointer = buf; 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 < 2) { fprintf(stderr,"usage: %s port_number1",argv[0]); exit(1); } sockfd = socket(AF_INET, SOCK_STREAM, 0); if (sockfd < 0) error("ERROR DETECTED !!! Problem in opening socket"); bzero((char *) &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 *) &serv_addr, sizeof(serv_addr)) < 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 *) &cli_addr, &clilen); if (newsockfd < 0) error("ERROR DETECTED !!! the connection request was not accepted"); int rc = read(newsockfd,&pointer,100); if(rc < 0){ printf("error"); } else { printf("success %d",rc); } for(int i=0;i<29;i++){ printf(pointer); printf(buf); } return 0; </code></pre> <p>}</p> <p>Client:</p> <pre><code> 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<MAXPROFILES;i++){ outObj.profiles[i].data = malloc(5); } for(i=0;i<4;i++){ outObj.src[i] = (srcAddress >> (i*8)) & 0xFF; outObj.dst[i] = (destAddress >> (i*8)) & 0xFF; } outObj.ver = 1; outObj.n = 2; memcpy(buf,&outObj.src,4); memcpy(buf+4,&outObj.dst,4); memcpy(buf+8,&outObj.ver,1); memcpy(buf+9,&outObj.n,2); outObj.profiles[0].length = 5; outObj.profiles[0].type = 1; outObj.profiles[1].length = 5; outObj.profiles[1].type = 2; for(i=0;i<MAXPROFILES;i++){ for(j=0;j<5;j++){ outObj.profiles[i].data[j] = j+1; } } int k = 11; for(i=0;i<MAXPROFILES;i++){ memcpy(buf+k,&outObj.profiles[0].length,1); memcpy(buf+k+1,&outObj.profiles[0].type,1); memcpy(buf+k+2,outObj.profiles[0].data,5); k +=7; } if (argc < 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 < 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 *) &serv_addr, sizeof(serv_addr)); //clear the memory for server address serv_addr.sin_family = AF_INET; bcopy((char *)server->h_addr, (char *)&serv_addr.sin_addr.s_addr, server->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 *)&serv_addr,sizeof(serv_addr)) < 0) error("ERROR in connection"); printf("SUCCESS !!! Connection established \n"); if (write(sockfd, buf, k) < 0) { error("Write error has occured "); } return 0; } </code></pre> <p>Now from the client side I do a memcpy to my unsigned char buf and send the data. On the recv side how to access the values inside my "buf". I tried the "*" operator, but i get a warning</p> <p>arning: passing argument 1 of âprintfâ makes pointer from integer without a cast</p> <p>I want to basically access the values inside buffer, as I know the size i should be able to repopulate my packet back. I know that this is a "C" question and not exactly "socket related". Any help would be really helpful.</p>

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