frido123

UDP server

学习网络编程时所写的一些代码，由于工作较忙，没太多功夫整理，也基本没有注释，如有疑问希望自己去查手册。这些程序都在linux下写的。

//使用recvmsg,和sendmsg进行收发

//udp-server2.c

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <netdb.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <string.h> #include <sys/select.h> #include <sys/time.h> #include <unistd.h> #include <errno.h> #define PORT 8848 #define BUFLEN 4096 typedef struct sockaddr sockaddr; typedef struct sockaddr_in sockaddr_in; typedef struct iovec iovec; typedef struct msghdr msghdr; typedef struct timeval timeval; int main(int argc, char *argv[]) { int sockfd; sockaddr_in rev_addr, send_addr; sockfd = socket(AF_INET, SOCK_DGRAM, IPPROTO_UDP); if(sockfd<0) { printf("error for socket()\n"); exit(1); } memset(&rev_addr, 0, sizeof(rev_addr)); rev_addr.sin_family = AF_INET; rev_addr.sin_port = htons(PORT); rev_addr.sin_addr.s_addr = htonl(INADDR_ANY); if(bind(sockfd, (sockaddr*)&rev_addr, sizeof(rev_addr)) < 0) { printf("error for bind()\n"); close(sockfd); exit(1); } while(1) { msghdr mh; iovec iov; char buf[1024]; int send_len = sizeof(send_addr); mh.msg_name = &send_addr; mh.msg_namelen = send_len; mh.msg_iov = &iov; mh.msg_iovlen = 1; mh.msg_iov->iov_base = buf; mh.msg_iov->iov_len = sizeof(buf); mh.msg_control = NULL; mh.msg_controllen = 0; mh.msg_flags = 0; int res; if((res = recvmsg(sockfd, &mh, 0))<0) { printf("error for recvmsg()%s\n", strerror(errno)); close(sockfd); exit(1); }else { printf("receive from %s:%u size:%d\n",inet_ntoa(send_addr.sin_addr), ntohs(send_addr.sin_port), strlen(buf)); } } return 0; }

//udp-server.c

//使用recvfrom,和sendto进行收发,效果和recvmsg/sendmsg一致

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <netdb.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <string.h> #define PORT 8848 #define BUFLEN 4096 int main(int argc, char *argv[]) { int sockfd; struct sockaddr_in my_addr; struct sockaddr_in dest_addr; char revbuf[BUFLEN]; sockfd = socket(AF_INET, SOCK_DGRAM, 0); if(sockfd<0) { printf("error for socket()\n"); exit(1); } memset(&my_addr, 0, sizeof(my_addr)); my_addr.sin_family = AF_INET; my_addr.sin_port = htons(PORT); my_addr.sin_addr.s_addr = htonl(INADDR_ANY);//inet_addr("200.200.30.14"); if(bind(sockfd, (struct sockaddr*)&my_addr, sizeof(my_addr)) < 0) { printf("error for bind()\n"); close(sockfd); exit(1); } while(1) { int revlen=0; int addr_len = sizeof(dest_addr); if((revlen=recvfrom(sockfd, revbuf, BUFLEN, 0, (struct sockaddr*)&dest_addr, &addr_len))<0) { printf("error for recvfrom()\n"); close(sockfd); exit(1); } else {//打印源 printf("receive from %s:%u\n",inet_ntoa(dest_addr.sin_addr), ntohs(dest_addr.sin_port)); /*struct sockaddr_in name;//打印其他数据信息 int len = sizeof(name); getsockname(sockfd, (struct sockaddr*)&name, &len); printf("sockname %s:%u\n", inet_ntoa(name.sin_addr), ntohs(name.sin_port)); memset(&name, 0, sizeof(name)); getpeername(sockfd, (struct sockaddr*)&name, &len); printf("peername %s:%u\n", inet_ntoa(name.sin_addr), ntohs(name.sin_port));*/ } if(sendto(sockfd, revbuf, revlen, 0, (struct sockaddr*)&dest_addr, sizeof(dest_addr))!=revlen) { printf("error for sendto()\n"); close(sockfd); exit(1); } else { //打印目的地 printf("send to %s:%u\n", inet_ntoa(dest_addr.sin_addr), ntohs(dest_addr.sin_port)); } } return 0; }

//rudp-server2.c

//rawsocket + sendto/recvfrom+修改头部

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <string.h> #include <errno.h> #define BUFLEN 4096 #define PORT 8848 typedef struct ip_hdr{ unsigned int ip_length:4; /*little-endian*/ unsigned int ip_version:4; unsigned char ip_tos; unsigned short ip_total_length; unsigned short ip_id; unsigned short ip_flags; unsigned char ip_ttl; unsigned char ip_protocol; unsigned short ip_cksum; unsigned int ip_source; unsigned int ip_dest; }ip_hdr; typedef struct udp_hdr{ unsigned short s_port; unsigned short d_port; unsigned short length; unsigned short cksum; }udp_hdr; typedef struct psd_header{//伪头部，用于计算校验和 unsigned int s_ip;//source ip unsigned int d_ip;//dest ip unsigned char mbz;//0 unsigned char proto;//proto type unsigned short plen;//length }psd_header; void swap(unsigned int *a, unsigned int *b) { *a = (*a)^(*b); *b = (*a)^(*b); *a = (*a)^(*b); } unsigned short checksum(unsigned short* buffer, int size) { unsigned long cksum = 0; while(size>1) { cksum += *buffer++; size -= sizeof(unsigned short); } if(size) { cksum += *(unsigned char*)buffer; } cksum = (cksum>>16) + (cksum&0xffff); //将高16bit与低16bit相加 cksum += (cksum>>16); //将进位到高位的16bit与低16bit 再相加 return (unsigned short)(~cksum); } int main(int argc, char *argv[]) { char revbuf[BUFLEN]; int sockfd = -1; struct sockaddr_in host_addr; if((sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_UDP))<0) { printf("socket() error!\n"); exit(1); } memset(&host_addr, 0, sizeof(host_addr)); host_addr.sin_family = AF_INET; host_addr.sin_port = htons(PORT); host_addr.sin_addr.s_addr = inet_addr("200.200.30.14"); if(bind(sockfd, (struct sockaddr*)&host_addr, sizeof(host_addr))<0) { printf("error for bind()%s\n", strerror(errno)); close(sockfd); exit(1); } const int on = 1; if(setsockopt(sockfd, IPPROTO_IP, IP_HDRINCL, &on, sizeof(on))<0) { printf("setsockopt() error!\n"); exit(0); } int addr_len = sizeof(host_addr); while(1) { int revlen=0; memset(&host_addr, 0, sizeof(host_addr)); int addr_len = sizeof(host_addr); if((revlen = recvfrom(sockfd, revbuf, BUFLEN, 0, (struct sockaddr*)&host_addr, &addr_len))<0) { printf("recvfrom() error!\n"); close(sockfd); exit(1); }else{ udp_hdr *udphdr; udphdr = (udp_hdr*)(revbuf+20); if(udphdr->d_port^htons(PORT)) continue; printf("receive from %s:%d\n", inet_ntoa(host_addr.sin_addr), ntohs(host_addr.sin_port)); struct sockaddr_in name; int len; getsockname(sockfd, (struct sockaddr*)&name, &len); printf("sockname %s:%d\n", inet_ntoa(name.sin_addr), ntohs(name.sin_port)); memset(&name, 0, sizeof(name)); getpeername(sockfd, (struct sockaddr*)&name, &len); printf("peername %s:%u\n", inet_ntoa(name.sin_addr), ntohs(name.sin_port)); ip_hdr *iphdr; iphdr = (ip_hdr*)revbuf; udp_hdr *udphdr1; udphdr1 = (udp_hdr*)(revbuf+20); swap(&(iphdr->ip_source), &(iphdr->ip_dest)); unsigned short t = udphdr1->s_port; udphdr1->s_port = udphdr1->d_port; udphdr1->d_port = htons(ntohs(t)+1); char tmp4[ntohs(udphdr1->length)+sizeof(psd_header)]; psd_header* ph = (psd_header*)tmp4; ph->d_ip=iphdr->ip_dest; ph->s_ip=iphdr->ip_source; ph->mbz=0; ph->proto = 0x11; ph->plen = udphdr1->length; //printf("udp header length %d\n", ntohs(udphdr1->length)); memcpy((unsigned char*)ph+sizeof(psd_header), (unsigned char*)udphdr1, ntohs(udphdr1->length)); udphdr1->cksum = 0; udphdr1->cksum = checksum((unsigned short*)(ph), ntohs(udphdr1->length)+sizeof(psd_header)); printf("totallen %d bytes\n", ntohs(iphdr->ip_total_length)); } if(sendto(sockfd, revbuf, revlen, 0, (struct sockaddr*)&host_addr, sizeof(host_addr))!=revlen) { printf("sendto() error, %s\n", strerror(errno)); close(sockfd)%

//交叉使用recvmsg,sendto

#include <stdio.h> #include <stdlib.h> #include <sys/types.h> #include <netdb.h> #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> #include <string.h> #include <sys/select.h> #include <sys/time.h> #include <unistd.h> #include <errno.h> #define PORT 8848 #define BUFLEN 4096 typedef struct sockaddr sockaddr; typedef struct sockaddr_in sockaddr_in; typedef struct iovec iovec; typedef struct msghdr msghdr; typedef struct timeval timeval; int main(int argc, char *argv[]) { int sockfd; sockaddr_in rev_addr, send_addr; sockfd = socket(AF_INET, SOCK_RAW, IPPROTO_UDP); if(sockfd<0) { printf("error for socket()\n"); exit(1); } while(1) { msghdr mh; iovec iov; char buf[1024]; int send_len = sizeof(send_addr); mh.msg_name = &send_addr; mh.msg_namelen = send_len; mh.msg_iov = &iov; mh.msg_iovlen = 1; mh.msg_iov->iov_base = buf; mh.msg_iov->iov_len = sizeof(buf); mh.msg_control = NULL; mh.msg_controllen = 0; mh.msg_flags = 0; int res; if((res = recvmsg(sockfd, &mh, 0))<0) { printf("error for recvmsg()%s\n", strerror(errno)); close(sockfd); exit(1); }else { printf("receive from %s:%u %c\n",inet_ntoa(send_addr.sin_addr), ntohs(send_addr.sin_port), buf[28]); } if(sendto(sockfd, revbuf, revlen, 0, (struct sockaddr*)&dest_addr, sizeof(dest_addr))!=revlen) { printf("error for sendto()\n"); close(sockfd); exit(1); }else { printf("send to %s:%u\n", inet_ntoa(dest_addr.sin_addr), ntohs(dest_addr.sin_port)); } } return 0; }

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UDP server

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