Not getting the exact data at server sent from client [closed] - c

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I am writing a client / server system in which the client sends a record from client to server. I am trying to represent the data as a struct, but I do not successfully recv() the struct at the server end.
Here is my code:
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <netdb.h>
#include <stdio.h>
#include <string.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <arpa/inet.h>
#pragma pack(1)
struct emp
{
int id;
char *name;
} emp1, emp3;
#pragma pack(0)
int main(int argc, char *argv[])
{
int sockfd = 0, n = 0;
char recvBuff[1024];
struct sockaddr_in serv_addr;
memset(recvBuff, '0', sizeof(recvBuff));
if ((sockfd = socket(AF_INET, SOCK_STREAM, 0)) < 0)
{
printf("\n Error : Could not create socket \n");
return 1;
}
memset(&serv_addr, '0', sizeof(serv_addr));
serv_addr.sin_family = AF_INET;
serv_addr.sin_port = htons(5000);
serv_addr.sin_addr = inet_addr("192.168.0.105");
if (inet_pton(AF_INET, argv[1], &serv_addr.sin_addr) <= 0)
{
printf("\n inet_pton error occured\n");
return 1;
}
if (connect(sockfd, (struct sockaddr *)&serv_addr, sizeof(serv_addr)) < 0)
{
printf("\n Error : Connect Failed \n");
return 1;
}
emp1 = (struct emp *) malloc(sizeof(struct emp));
emp1.name = (char *) malloc((size)*(sizeof(char)));
printf("Enter name of employee : ");
scanf(" %[^\n]s", emp1.name);
printf("Enter emp id : ");
scanf(" %d", &emp1.id);
unsigned char *data = (unsigned char*) malloc(sizeof(regn));
memcpy(data, &regn, sizeof(regn));
sendto(sockfd, data, sizeof(emp1), 0, (SOCKADDR *) &serv_addr,
sizeof(serv_addr));
close(sockfd);
}
and my server is like this
#include <sys/socket.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <sys/types.h>
#include <time.h>
struct emp
{
int id;
char *name;
} emp1, emp3;
int main(int argc, char *argv[])
{
int listenfd = 0, connfd = 0;
struct sockaddr_in serv_addr;
FILE *fp, *fp1;
char recvBuf[1025];
listenfd = socket(AF_INET, SOCK_STREAM, 0);
memset(&serv_addr, '0', sizeof(serv_addr));
memset(sendBuff, '0', sizeof(sendBuff));
serv_addr.sin_family = AF_INET;
serv_addr.sin_addr.s_addr = htonl(INADDR_ANY);
serv_addr.sin_port = htons(5000);
bind(listenfd, (struct sockaddr*)&serv_addr, sizeof(serv_addr));
listen(listenfd, 10);
connfd = accept(listenfd, (struct sockaddr*)NULL, NULL);
if(recvfrom(sd, recvBuf, recvBufSize, 0,
(struct sockaddr *) &clientAddr, &len) < 0)
{
printf("Error receiving message from client\n");
}
else
{
printf("Message received:%s\n", recvBuf);
printf("Size :%d\n", strlen(recvBuf));
memcpy(&emp1, recvBuf, sizeof(emp));
printf("name:%s\n", emp1.name );
printf("is:%d\n", emp1.id);
}

Answer 1

you are sending a struct which contains an integer and a char pointer. This pointer points to a completly random location, on the receiving system.
You have to send the content name points to.
You could send every member of the struct on its own. For members with variable length, you have to send the size first and allocate it on the receiving end.
As stated by John Bollinger: One of your structs is packed, the other not. this may cause additional problems with layout and size of the struct and is probably unnecessary .

Answer 2

Added this answer to answer to specific questions of the OP (it may seem a bit off track of the original question).
An example of simple streaming. It is simple because in a real streaming scenario you need object id's to be able to instantiate and load the real classes. But if you know already what class you are sending or receiving, their is no need for this complexity. If you are sending multiple instances of classes then you need a more complex streaming mechanism. As microsoft did for instance in MFC, Borland in OWL, .NET also has mechanisms in place, ...
namespace OMCIPoco{
typedef std::vector<unsigned char> ucharvector;
SystemData::stream& operator <<(SystemData::stream& stream,const ucharvector& data);
SystemData::stream& operator >>(SystemData::stream& stream,ucharvector& data);
}
The cpp file :
SystemData::stream& operator <<(SystemData::stream& stream,const ucharvector& data)
{
stream << (unsigned long)data.size();
for (ucharvector::const_iterator it=data.begin();it<data.end();++it)
stream << *it;
return stream;
}
SystemData::stream& operator >>(SystemData::stream& stream,ucharvector& data)
{
unsigned long count;
stream >> count;
data.reserve(count);
for (unsigned int i=0;i<count;++i){
unsigned char c;
stream >> c;
data.push_back(c);
}
return stream;
}
Notice how the << and >> are in balance.
The stream is an interface that makes abstraction of the medium you are streaming to, it can be memory or disk or a networkstream. I can solve little endian problems using the streaming concept here as well, because the stream knows how to (de)serialise shorts, longs, ..., and it knows howto buffer as well.
You can use a flat structure as well avoiding the above complexity completely
class data{
public:
char name[20];
};
now using sizeof(data) will be correct because you will send the entire data struct. I used class here but struct works just the same way. The downside is that if the name contains only 10 charakters you will still send 20.