服务器端代码如果采用fork写时复制(Copy on Write)技术，代码还可以更简洁一点
服务端代码：
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <netdb.h>
#include <arpa/inet.h>
#define BUFSIZE 4096
#define CHILD_PORT_START 16500
const char* Inet_ntop(void* ptr) {
static char str[INET_ADDRSTRLEN];
return inet_ntop(AF_INET,ptr,str,INET_ADDRSTRLEN);
}
void server_echo(int sockfd) {
int fullfd[2];
if (socketpair(AF_UNIX,SOCK_DGRAM,0,fullfd) < 0) {
printf("sockpair error: %s\n",strerror(errno));
exit(1);
}
char recv[BUFSIZE];
struct sockaddr_in clientaddr;
socklen_t len = sizeof(struct sockaddr_in);
ssize_t n;
struct iovec iov[2];
int pid;
for (; ;) {
if ((n = recvfrom(sockfd,recv,BUFSIZE,0,(struct sockaddr*)&clientaddr,&len)) < 0) {
printf("receive from client error: %s\n",strerror(errno));
break;
}
iov[0].iov_base = &clientaddr;
iov[0].iov_len = len;
iov[1].iov_base = recv;
iov[1].iov_len = n;
if (writev(fullfd[0],iov,2) != n + len) {
printf("writev to child error: %s\n",strerror(errno));
exit(1);
}
if ((pid = fork()) < 0) {
printf("fork error: %s\n",strerror(errno));
break;
}else if (pid == 0) {
struct sockaddr_in to;
socklen_t tolen = sizeof(struct sockaddr_in);
int childfd;
struct sockaddr_in server;
server.sin_family = AF_INET;
server.sin_port = getpid() - getppid() + CHILD_PORT_START;
server.sin_addr.s_addr = htonl(INADDR_ANY);
struct iovec get[2];
char send[BUFSIZE];
ssize_t count = n;
get[0].iov_base = &to;
get[0].iov_len = sizeof(struct sockaddr_in);
get[1].iov_base = send;
get[1].iov_len = BUFSIZE;
if (readv(fullfd[1],get,2) != count + tolen) {
printf("readv error: %s\n",strerror(errno));
exit(1);
}
printf("child process pid = %d handle from IP: %s client\n",getpid(),Inet_ntop(&to.sin_addr));
if ((childfd = socket(AF_INET,SOCK_DGRAM,IPPROTO_UDP)) < 0) {
printf("child socket error: %s\n",strerror(errno));
}
if (bind(childfd,(struct sockaddr*)&server,sizeof(struct sockaddr_in)) < 0) {
printf("child bind error: %s\n",strerror(errno));
exit(1);
}
if (sendto(childfd,send,count,0,(struct sockaddr*)&to,tolen) != count) {
printf("send to error: %s\n",strerror(errno));
exit(1);
}
while ((count = recvfrom(childfd,send,BUFSIZE,0,(struct sockaddr*)&to,&tolen)) > 0) {
if (sendto(childfd,send,count,0,(struct sockaddr*)&to,tolen) != count) {
printf("send to client error: %s\n",strerror(errno));
exit(1);
}
}
}
}
}
int main(int argc,char** argv) {
if (argc != 2) {
printf("please add or check <service name>\n");
exit(1);
}
struct addrinfo hints;
bzero(&hints,sizeof(struct addrinfo));
hints.ai_flags = AI_PASSIVE;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_DGRAM;
hints.ai_protocol = IPPROTO_UDP;
struct addrinfo* results;
int err;
if ((err = getaddrinfo(NULL,argv[1],&hints,&results)) != 0) {
printf("getaddrinfo error: %s\n",gai_strerror(err));
exit(1);
}
struct addrinfo* dummy = results;
int sockfd;
for (; dummy != NULL; dummy = dummy->ai_next) {
if ((sockfd = socket(dummy->ai_family,dummy->ai_socktype,dummy->ai_protocol)) < 0) {
continue;
}
if (ntohs(((struct sockaddr_in*)dummy->ai_addr)->sin_port) >= CHILD_PORT_START) {
printf("Warnning：Dangerous use the port,if have many client,so you should use less than the port try once again\n");
close(sockfd);
exit(1);
}
if (bind(sockfd,dummy->ai_addr,dummy->ai_addrlen) == 0) {
break;
}
close(sockfd);
}
server_echo(sockfd);
return 0;
}客户端代码:
#include <stdio.h>
#include <stdlib.h>
#include <sys/socket.h>
#include <unistd.h>
#include <string.h>
#include <errno.h>
#include <netdb.h>
#define BUFSIZE 4096
void client_echo(int sockfd,struct sockaddr* to,socklen_t tolen) {
char send[BUFSIZE];
ssize_t n;
struct sockaddr_in clientaddr;
const int on = 1;
socklen_t len = sizeof(struct sockaddr_in);
if (setsockopt(sockfd,SOL_SOCKET,SO_BROADCAST,&on,sizeof(on)) < 0) {
printf("setsockopt error: %s\n",strerror(errno));
exit(1);
}
while ((n = read(STDIN_FILENO,send,BUFSIZE)) > 0) {
if (sendto(sockfd,send,n,0,to,tolen) != n) {
printf("sendto error: %s\n",strerror(errno));
exit(1);
}
if (recvfrom(sockfd,send,BUFSIZE,0,(struct sockaddr*)&clientaddr,&len) != n) {
printf("recv from server error: %s\n",strerror(errno));
exit(1);
}
struct sockaddr_in *dummy = (struct sockaddr_in*)to;
dummy->sin_port = clientaddr.sin_port;
if (write(STDOUT_FILENO,send,n) != n) {
printf("write error: %s\n",strerror(errno));
exit(1);
}
}
}
int main(int argc,char** argv) {
if (argc != 3) {
printf("please add <ip address-host name> <service name or port name>\n");
exit(1);
}
struct addrinfo hints;
bzero(&hints,sizeof(struct addrinfo));
hints.ai_flags = AI_ALL;
hints.ai_family = AF_INET;
hints.ai_socktype = SOCK_DGRAM;
hints.ai_protocol = IPPROTO_UDP;
struct addrinfo* results;
int err;
if ((err = getaddrinfo(argv[1],argv[2],&hints,&results)) != 0) {
printf("getaddrinfo error: %s\n",gai_strerror(err));
exit(1);
}
struct addrinfo* dummy = results;
int sockfd;
for (; dummy != NULL; dummy = dummy->ai_next) {
if ((sockfd = socket(dummy->ai_family,dummy->ai_socktype,dummy->ai_protocol)) < 0) {
continue;
}else {
break;
}
}
if (dummy == NULL) {
freeaddrinfo(results);
printf("all socket failed\n");
exit(1);
}
client_echo(sockfd,dummy->ai_addr,dummy->ai_addrlen);
freeaddrinfo(results);
}