在我的套接字代码中,我有以下结构:
服务器:
#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;
客户:
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;
}
现在我从客户端对我的 unsigned char buf 执行 memcpy 并发送数据。在 recv 端如何访问我的“buf”中的值。我尝试了“*”运算符,但收到警告
学习:传递“printf”的参数 1 从整数生成指针,无需强制转换
我想基本上访问缓冲区内的值,因为我知道我应该能够重新填充我的数据包的大小。我知道这是一个“C”问题而不是完全“套接字相关”。任何帮助都会非常有帮助。
最佳答案
在服务器端,你只需要反转你在客户端所做的:
使用 char *pointer = buf
也不会获得任何好处,只是直接读入缓冲区。当你为你的 MAXPROFILES
循环时,只需检查你在 buffer
中的当前位置与返回的 size
以确保你没有读取你的数据没收到。
例如:
int size = read(newsockfd, buffer, sizeof(buffer));
int src, dst;
char ver;
short n;
memcpy(&src, buf + 0, 4);
memcpy(&dst, buf + 4, 4);
memcpy(&ver, buf + 8, 1);
memcpy(&n, buf + 9, 2);
……等等……
您在客户端对您的结构/数据进行编码,因此您必须在服务器端对它们进行解码。一旦你这样做了,你就可以打印它们或做任何你喜欢的事情:
printf("src: %d dst: %d ver: %c n: %d\n", src, dst, ver, n);
此外,为了简化您的编码/解码,请使用相同的方法(例如,memcpy
而不是您的带掩码的逐字节方法)。例如,在客户端:
k = 0;
memcpy(buf + k, &src, sizeof(src)); k += sizeof(src);
memcpy(buf + k, &dst, sizeof(dst)); k += sizeof(dst);
...
这也让您从硬编码数字中解脱出来,就像我在上面所做的那样。只需确保您的 src
、dst
以及所有其他内容在客户端和服务器上都具有相同的类型。
关于c - 在套接字中使用 read() 访问缓冲区,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/6854311/