Getting segfault due to string data type variable

When I am sending a protobuf variable through socket communication on recv end I am trying to display the string variable of protobuf I got segmentation in this remaining Data type other than String they are working fine but string variable case I got segmentation How can I over come in Protobuf string datatype segmentation fault other than we have any other data type for store the string data type.

I create a example.proto with in string variable name is there I am compile example.proto with protoc compiler (protoc example.proto --cpp_out <path>) it create two files two files example.pb.h, example.pb.cc By using these files I create a test_server.cpp and test_client.cpp And compile it. but at the time of both programms runing I sent a protobuf variable on recv side it give segmentation fault due to trying to display string variable.

How can I solve this problem?

example.proto

package data;
message  star
{ optional string name=1; }

server.cpp

#include<iostream>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<strings.h>
#include<string.h>
#include <arpa/inet.h>
#include"example.pb.h"
#include"example.pb.cc"

int main() 
{ 
    int sd,csd;
    sd=socket(AF_INET, SOCK_STREAM,0);
    perror("socket");
    sockaddr_in ser,cli;
    ser.sin_family=AF_INET;
    ser.sin_port=htons(7878);
    ser.sin_addr.s_addr=inet_addr("X.Y.Z.A");
    bzero(ser.sin_zero, 8);
    size_t s=16;

    if(bind(sd,(struct sockaddr *)&ser, s)==-1)
        cout<<"Bind FAIL\n";
    else
        cout<<"Bind Success\n";

    if((csd=accept(sd,(struct sockaddr *)&cli, &s))==-1)
        cout<<"Connection Accept FAIL\n";
    else
        cout<<"ConnectioN Accept Success\n";

    star pkt;
    recv(csd,&pkt,sizeof(pkt),0);
    cout<<"\t String Name: "<<pkt.name<<endl; //Here only i get segmentation
    close(sd);
    close(csd);
}

client.cpp

#include<iostream>
#include<sys/types.h>
#include<sys/socket.h>
#include<netinet/in.h>
#include<strings.h>
#include<string.h>
#include <arpa/inet.h>
#include"example.pb.h"
#include"example.pb.cc"

int main()
{
    int sd;
    sd=socket(AF_INET, SOCK_STREAM,0);
    perror("socket");
    sockaddr_in ser;
    ser.sin_family=AF_INET;
    ser.sin_port=htons(7878);
    ser.sin_addr.s_addr=inet_addr("X.Y.Z.A");
    bzero(ser.sin_zero, 8);

    if(connect(sd,(struct sockaddr *)&ser, 16)==-1)
        cout<<"connect FAIL\n";
    else
        cout<<"connect Success\n";

    star pkt;
    pkt.set_name("Pratap");
    cout<<"Send Data without help of another variable....\n";
    send(sd,&pkt,sizeof(pkt) ,MSG_CONFIRM);
    close(sd);
}

Your problem is here:

star pkt;
recv(csd,&pkt,sizeof(pkt),0);

and here:

star pkt;
pkt.set_name("Pratap");
cout<<"Send Data without help of another variable....\n";
send(sd,&pkt,sizeof(pkt) ,MSG_CONFIRM);

You can't receive/send the star instance directly without de/serializing it from/to protobuf wire format first. Have a look at the ParseFrom SerializeTo methods of the protobuf::MessageLite class.

The best way is to send the length of the serialized message first in a fixed format (e.g. a uint32_t in network byte order). Then the receiver can read this first and allocate a buffer of the appropriate size before receiving the serialized message that is send afterwards.

UPDATE:
Try s.th. like this:

Sender.cpp

star pbMsgObj;
pbMsgObj.set_name("Pratap");

std::string pkt;
pbMsgObj.SerializeToString(&pkt); // Serialize the message object to 
                                  // protobuf wire format.
uint32_t msgLength = pkt.size();
uint32_t sndMsgLength = htonl(msg_length); // Ensure network byte order

send(sd,&sndMsgLength ,sizeof(uint32_t) ,MSG_CONFIRM); // Send the message length
send(sd,pkt.c_str() ,msgLength ,MSG_CONFIRM); // Send the message data

Receiver.cpp

star msgObject;
uint32_t msgLength;
recv(csd,&msgLength,sizeof(uint32_t),0); // Receive the message length
msgLength = ntohl(msgLength); // Ensure host system byte order

std::vector<uint8_t> pkt; // Allocate a receive buffer
pkt.resize(msgLength,0x00);

recv(csd,&(pkt[0]),msgLength,0); // Receive the message data
std::string tmp;
tmp.assign(&(pkt[0]),pkt.size()); // Convert message data to a string

msgObject.ParseFromString(tmp); // Deserialize the message object from
                                // protobuf wire format.

NOTE:
De-/Serializing from/to a unique, efficient wire format used with various language bindings is the whole point of google protocol buffers.

For twiddling out the bits of possible sender/receiver patterns, instead of creating 'raw' sockets you might find 0MQ being a useful framework. Anyway listen to good advice(!): Keep message (payload) format and send/recv behavior as separate as possible.