c++ - Partial udp file transfer -

i have following basic c++ code transferring file via udp using sockets on linux. problem is, not packets gets delivered (like 8 bytes out of 345kb received), know udp unreliable have code or because of udp's unreliability?

client side

sockfd=socket(af_inet,sock_dgram,0);  bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = af_inet; servaddr.sin_addr.s_addr=inet_addr("192.168.0.152"); servaddr.sin_port=htons(32000); ifstream myfile("345kb.doc", ios::in); int i=0; char* memblock; double size; if(myfile.is_open()) {     myfile.seekg(0,ios::end);     size=(double)myfile.tellg();     memblock=new char[1024];     myfile.seekg(0,ios::beg);     double filesize=size;     cout<<filesize;     int n;     int ab=(int)filesize%1024;     while(filesize>1024){         myfile.read(memblock,1024);         cout<<"\nread:"<<strlen(memblock)<<"\n"<<"sent:";         n=sendto(sockfd,memblock,strlen(memblock),0,(struct sockaddr *)&servaddr,sizeof(servaddr));         filesize=filesize-1024;         cout<<n<<"\n";     }     myfile.read(memblock,1024);     n=sendto(sockfd,memblock,strlen(memblock),0,(struct sockaddr *)&servaddr,sizeof(servaddr));     std::cout<<"hi"<<endl; } else {     printf("\nfile not opened \n"); } 

server side

int sockfd,n; struct sockaddr_in servaddr,cliaddr; socklen_t len; char mesg[1024];  sockfd=socket(af_inet,sock_dgram,0);  bzero(&servaddr,sizeof(servaddr)); servaddr.sin_family = af_inet; servaddr.sin_addr.s_addr=htonl(inaddr_any); servaddr.sin_port=htons(32000); bind(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr));  //for (;;) //{     ofstream myfile;     myfile.open("345kbsssss.doc",ios::out|ios::app);     if(myfile.is_open()) {         long i=0;         len = sizeof(cliaddr);         while((n = recvfrom(sockfd,mesg,1024,0,(struct sockaddr *)&cliaddr,&len))>0){             std::cout<<"hi\n";             //n=recvfrom(sockfd,mesg,256,0,(struct sockaddr *)&cliaddr,&len);             myfile.write(mesg,n);         }     }     else printf("\nfile not created\n"); //} 

both true:

• udp not meant used file transfer without implementing checking, reordering , retransmission. instead of implementing these on udp, better switch tcp. rare exception of resource limited embedded systems.

• in code use strlen block length, since file (most probably) binary producing incorrect length values , not transmit whole file data. strlen operates on 0 terminated strings , counts first 0 byte in data.

to more correct results, easiest way replace strlen(memblock) min(1024,filesize). not perfect solution because not check how many bytes read myfile.read.