粘包及处理方法
粘包：由于缓冲区及下层硬件的原因，第n个包与第n+1个包合并在一起发送，或第n个包与第n+1个包的一部分合并在一起发送，等等。如果接收方要求格式良好，那我们就必须控制发送与接收方式。
处理方法：
1.发送定长包，发送方每次固定发送n个字节长，同时接受方固定每次读n个字节长。缺点：数据不长时，浪费宽带和低效率。
2.发送包头+包体，先发送定长的n字节包头(用于表示数据长度)，再发送由包头中所指定长度的数据
3.以行('
')为单位进行读取
定长包
在2.5版添加如下函数,然后在main函数中将read/write修改为readn和writen即可
ssize_t readn(int fd,void *buff,size_t count){
char *buffp;
ssize_t nread;
size_t nleft;
buffp=(char *)buff;
nleft=count;
while(nleft > 0){
if((nread = read(fd,buffp,nleft)) < 0){
if(errno == EINTR)
continue;
else
return -1;
}else if(nread == 0)
break;
nleft -= nread;
buffp += nread;
}
return count-nleft;
}
ssize_t writen(int fd,const void *buff,size_t n){
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr=buff;
nleft=n;
while(nleft > 0){
if((nwritten=write(fd,ptr,nleft)) < 0){
if(nwritten < 0 && errno == EINTR)
continue;
else
return -1;
}else if(nwritten == 0)
break;
nleft -= nwritten;
ptr += nwritten;
}
return n-nleft;
}
包头+包体
注意点:包头中定义包体的长度的int需要以网络字节序来记录, 所以在发送时要用htonl,在接收时要用ntohl
server.c
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
void err_quit(const char *s){
perror(s);
exit(1);
}
void handler(int signo){
printf("program terminated
");
exit(0);
}
struct packet{
int len;
char buf[1024];
};
ssize_t readn(int fd,void *buff,size_t count){
char *buffp;
ssize_t nread;
size_t nleft;
buffp=(char *)buff;
nleft=count;
while(nleft > 0){
if((nread = read(fd,buffp,nleft)) < 0){
if(errno == EINTR)
continue;
else
return -1;
}else if(nread == 0)
break;
nleft -= nread;
buffp += nread;
}
return count-nleft;
}
ssize_t writen(int fd,const void *buff,size_t n){
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr=buff;
nleft=n;
while(nleft > 0){
if((nwritten=write(fd,ptr,nleft)) < 0){
if(nwritten < 0 && errno == EINTR)
continue;
else
return -1;
}else if(nwritten == 0)
break;
nleft -= nwritten;
ptr += nwritten;
}
return n-nleft;
}
int main(int argc,char *argv[]){
int sockfd,connfd;
pid_t child;
socklen_t len;
struct sockaddr_in addr,client;
if((sockfd=socket(PF_INET,SOCK_STREAM,0)) < 0)
err_quit("sockfd");
bzero(&addr,sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_addr.s_addr=htonl(INADDR_ANY);
addr.sin_port=htons(5566);
int on=1;
if(setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on)) <0)
err_quit("setsockopt");
if(bind(sockfd,(struct sockaddr *)&addr,sizeof(addr))<0)
err_quit("bind");
if(listen(sockfd,10)<0)
err_quit("listen");
len=sizeof(client);
connfd=accept(sockfd,(struct sockaddr *)&client,&len);
if(connfd < 0)
err_quit("accept");
struct packet pac;
bzero(&pac,sizeof(pac));
int n;
if((child=fork())<0){
err_quit("fork");
}else if(child == 0){
while(1){
int ret=readn(connfd,&pac.len,4);
if(ret == -1)
err_quit("read");
else if(ret < 4){
printf("peer closed
");
break;
}
n=ntohl(pac.len);
ret=readn(connfd,pac.buf,n);
if(ret < 1){
err_quit("read");
}
if(ret < n){
printf("peer closed
");
break;
}
fputs(pac.buf,stdout);
bzero(&pac,sizeof(pac));
}
kill(getppid(),SIGUSR1);
}else{
signal(SIGUSR1,handler);
while(fgets(pac.buf,sizeof(pac.buf),stdin) != NULL){
n=strlen(pac.buf);
pac.len=htonl(n);
writen(connfd,&pac,n+4);
}
}
exit(0);
}
client.c
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
void err_quit(const char *s){
perror(s);
exit(1);
}
void handler(int signo){
printf("program terminated
");
exit(0);
}
struct packet{
int len;
char buf[1024];
};
ssize_t readn(int fd,void *buff,size_t count){
size_t nleft;
ssize_t nread;
char *ptr;
nleft=count;
ptr=(char *)buff;
while(nleft > 0){
if((nread=read(fd,ptr,nleft)) < 0){
if(errno == EINTR)
continue;
else
return -1;
}else if(nread == 0)
break;
ptr += nread;
nleft -= nread;
}
return count - nleft;
}
ssize_t writen(int fd,const void *buff,size_t n){
size_t nleft;
ssize_t nwritten;
const char *ptr;
nleft=n;
while(n > 0){
if((nwritten=write(fd,buff,nleft)) < 0){
if(errno == EINTR)
continue;
else
return -1;
}else if(nwritten == 0)
break;
nleft -= nwritten;
ptr += nwritten;
}
return n-nleft;
}
int main(int argc,char *argv[]){
int sockfd;
struct sockaddr_in servaddr;
pid_t child;
if((sockfd=socket(PF_INET,SOCK_STREAM,0)) < 0)
err_quit("socket");
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servaddr.sin_port=htons(5566);
if(connect(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr)) <0)
err_quit("connect");
struct packet pac;
bzero(&pac,sizeof(pac));
int n;
if((child=fork()) <0)
err_quit("fork");
else if(child == 0){
signal(SIGUSR1,handler);
while(fgets(pac.buf,sizeof(pac.buf),stdin) != NULL){
n=strlen(pac.buf);
pac.len=htonl(n);
writen(sockfd,&pac,n+4);
}
}else{
while(1){
int ret=readn(sockfd,&pac.len,4);
if(ret == -1)
err_quit("read");
if(ret < 4){
printf("perr closed
");
break;
}
n=ntohl(pac.len);
ret=readn(sockfd,pac.buf,n);
if(ret == -1)
err_quit("read");
if(ret < n){
printf("peer closed
");
break;
}
fputs(pac.buf,stdout);
bzero(&pac,sizeof(pac));
}
kill(child,SIGUSR1);
}
exit(0);
}
行为单位进行读取
非常适用于终端消息的性状
server.c
#include <unistd.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <signal.h>
#include <sys/wait.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
void err_quit(const char *s){
perror(s);
exit(1);
}
void handler(int signo){
printf("program terminated
");
exit(0);
}
ssize_t readn(int fd,void *buff,size_t count){
char *buffp;
ssize_t nread;
size_t nleft;
buffp=(char *)buff;
nleft=count;
while(nleft > 0){
if((nread = read(fd,buffp,nleft)) < 0){
if(errno == EINTR)
continue;
else
return -1;
}else if(nread == 0)
break;
nleft -= nread;
buffp += nread;
}
return count-nleft;
}
ssize_t writen(int fd,const void *buff,size_t n){
size_t nleft;
ssize_t nwritten;
const char *ptr;
ptr=buff;
nleft=n;
while(nleft > 0){
if((nwritten=write(fd,ptr,nleft)) < 0){
if(nwritten < 0 && errno == EINTR)
continue;
else
return -1;
}else if(nwritten == 0)
break;
nleft -= nwritten;
ptr += nwritten;
}
return n-nleft;
}
ssize_t recv_peek(int fd,void *buf,size_t len){
ssize_t ret;
while(1){
ret=recv(fd,buf,len,MSG_PEEK);
if(ret == -1 && errno == EINTR)
continue;
return ret;
}
}
ssize_t readline(int fd,void *buf,size_t maxline){
ssize_t ret;
size_t nread;
size_t nleft;
char *bufp;
bufp=buf;
nleft=maxline;
while(1){
ret=recv_peek(fd,buf,nleft);
if(ret < 0)
return ret;
else if(ret == 0)
return ret;
nread=ret;
int i;
for(i=0;i<nread;i++){
if(bufp[i] == '
'){
ret=readn(fd,bufp,i+1);
if(ret != i+1)
err_quit("readn");
return ret;
}
}
if(nread > nleft)
err_quit("readn");
nleft -= nread;
ret=readn(fd,bufp,nread);
if(ret != nread)
err_quit("readn");
bufp += nread;
}
return -1;
}
int main(int argc,char *argv[]){
int sockfd,connfd;
pid_t child;
socklen_t len;
struct sockaddr_in addr,client;
if((sockfd=socket(PF_INET,SOCK_STREAM,0)) < 0)
err_quit("sockfd");
bzero(&addr,sizeof(addr));
addr.sin_family=AF_INET;
addr.sin_addr.s_addr=htonl(INADDR_ANY);
addr.sin_port=htons(5566);
int on=1;
if(setsockopt(sockfd,SOL_SOCKET,SO_REUSEADDR,&on,sizeof(on)) <0)
err_quit("setsockopt");
if(bind(sockfd,(struct sockaddr *)&addr,sizeof(addr))<0)
err_quit("bind");
if(listen(sockfd,10)<0)
err_quit("listen");
len=sizeof(client);
connfd=accept(sockfd,(struct sockaddr *)&client,&len);
if(connfd < 0)
err_quit("accept");
char buf[1024];
bzero(buf,sizeof(buf));
if((child=fork())<0){
err_quit("fork");
}else if(child == 0){
while(1){
int ret=readline(connfd,buf,sizeof(buf));
if(ret == -1)
err_quit("readline");
else if(ret == 0){
printf("peer closed
");
break;
}
fputs(buf,stdout);
bzero(buf,sizeof(buf));
}
kill(getppid(),SIGUSR1);
}else{
signal(SIGUSR1,handler);
while(fgets(buf,sizeof(buf),stdin) != NULL){
writen(connfd,buf,strlen(buf));
}
}
exit(0);
}
client.c
#include <unistd.h>
#include <signal.h>
#include <errno.h>
#include <stdlib.h>
#include <stdio.h>
#include <string.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <arpa/inet.h>
#include <netinet/in.h>
void err_quit(const char *s){
perror(s);
exit(1);
}
void handler(int signo){
printf("program terminated
");
exit(0);
}
ssize_t readn(int fd,void *buff,size_t count){
size_t nleft;
ssize_t nread;
char *ptr;
nleft=count;
ptr=(char *)buff;
while(nleft > 0){
if((nread=read(fd,ptr,nleft)) < 0){
if(errno == EINTR)
continue;
else
return -1;
}else if(nread == 0)
break;
ptr += nread;
nleft -= nread;
}
return count - nleft;
}
ssize_t writen(int fd,const void *buff,size_t n){
size_t nleft;
ssize_t nwritten;
const char *ptr;
nleft=n;
while(n > 0){
if((nwritten=write(fd,buff,nleft)) < 0){
if(errno == EINTR)
continue;
else
return -1;
}else if(nwritten == 0)
break;
nleft -= nwritten;
ptr += nwritten;
}
return n-nleft;
}
/* if have any data then return */
ssize_t recv_peek(int fd,void *buf,size_t len){
ssize_t ret;
while(1){
ret=recv(fd,buf,len,MSG_PEEK);
if(ret == -1 && errno == EINTR)
continue;
return ret;
}
}
ssize_t readline(int fd,void *buf,size_t maxline){
ssize_t ret;
size_t nread;
size_t nleft;
char *bufp;
bufp=buf;
nleft=maxline;
while(1){
ret=recv_peek(fd,buf,nleft);
if(ret < 0)
return ret;
else if(ret == 0)
return ret;
nread=ret;
int i;
for(i=0;i<nread;i++){
if(bufp[i] == '
'){
ret=readn(fd,bufp,i+1);
if(ret != i+1)
err_quit("readn");
return ret;
}
}
if(nread > nleft)
err_quit("nread");
nleft -= nread;
ret=readn(fd,bufp,nread);
if(ret != nread)
err_quit("readn");
bufp += nread;
}
return -1;
}
int main(int argc,char *argv[]){
int sockfd;
struct sockaddr_in servaddr;
pid_t child;
if((sockfd=socket(PF_INET,SOCK_STREAM,0)) < 0)
err_quit("socket");
bzero(&servaddr,sizeof(servaddr));
servaddr.sin_family=AF_INET;
servaddr.sin_addr.s_addr=inet_addr("127.0.0.1");
servaddr.sin_port=htons(5566);
if(connect(sockfd,(struct sockaddr *)&servaddr,sizeof(servaddr)) <0)
err_quit("connect");
char buf[1024];
bzero(buf,sizeof(buf));
if((child=fork()) <0)
err_quit("fork");
else if(child == 0){
signal(SIGUSR1,handler);
while(fgets(buf,sizeof(buf),stdin) != NULL){
writen(sockfd,buf,strlen(buf));
}
}else{
while(1){
int ret=readline(sockfd,buf,sizeof(buf));
if(ret == -1)
err_quit("readline");
if(ret == 0){
printf("peer closed
");
break;
}
fputs(buf,stdout);
bzero(buf,sizeof(buf));
}
kill(child,SIGUSR1);
}
exit(0);
}