流协议与粘包

TCP：基于字节流的传输服务，无边界，不能保证对等方一次接受能能够返回好多字节
UDP：基于消息的传输服务，传输数据包有边界
粘包产生的原因：
粘包解决方案：
- 定长包
- 包尾加（ftp)
- 包头加上包体长度
- 更复杂的应用层协议

readn writen(广域网必须处理粘包问题)

service

  1 #include <stdio.h>
  2 #include <errno.h>
  3 #include <string.h>
  4 #include <stdlib.h>
  5 #include <unistd.h>
  6 #include <sys/types.h>
  7 #include <sys/socket.h>
  8 #include <netinet/in.h>
  9 #include <arpa/inet.h>
 10 
 11 #define ERR_EXIT(m)
 12     do{
 13         perror(m);
 14         exit(EXIT_FAILURE);
 15     }while(0)
 16 
 17 struct packet
 18 {
 19     int len;
 20     char buf[1024];
 21 };
 22 
 23 ssize_t readn(int fd, void* buf,size_t count)
 24 {
 25     size_t nleft = count;
 26     ssize_t nread;
 27     char *bufp = (char*)buf;
 28     
 29     while(nleft > 0)
 30     {
 31         if((nread = read(fd,bufp,nleft)) < 0)
 32         {
 33             if(errno == EINTR)
 34                 continue;
 35             return -1;
 36         }
 37         else if(nread == 0)
 38         {
 39             return count-nleft;
 40         }
 41         
 42         bufp += nread;
 43         nleft -= nread;
 44     }
 45     return count;
 46 }
 47 
 48 ssize_t writen(int fd, void* buf,size_t count)
 49 {
 50     size_t nleft = count;
 51     ssize_t nwrite;
 52     char *bufp = (char*)buf;
 53     
 54     while(nleft > 0)
 55     {
 56         if((nwrite = write(fd,bufp,nleft)) < 0)
 57         {
 58             if (errno = EINTR)
 59                 continue;
 60             return -1;
 61         }
 62         else if(nwrite == 0)
 63             continue;
 64         bufp += nwrite;
 65         nleft -= nwrite;
 66     }    
 67     return count;
 68 }
 69 
 70 void do_service(int conn)
 71 {
 72 //    char recvbuf[1024];
 73     struct packet recvbuf;
 74     int n;
 75     while(1)
 76     {
 77         memset(&recvbuf,0,sizeof(recvbuf));
 78         int ret = readn(conn,&recvbuf.len,4);
 79         if(ret < 4)
 80         {
 81             printf("client close
");
 82             break;
 83         }
 84         else if(ret == -1)
 85             ERR_EXIT("read");
 86         n = ntohl(recvbuf.len);
 87         ret = readn(conn,&recvbuf.buf,n);
 88         if(ret == -1)
 89             ERR_EXIT("read");
 90         else if(ret < n)
 91         {
 92             printf("client close
");
 93             break;
 94         }
 95                 
 96         fputs(recvbuf.buf,stdout);
 97         writen(conn,&recvbuf,n+4);
 98     }
 99 }
100 
101 int main(void)
102 {
103     int listenfd;
104     if((listenfd = socket(AF_INET,SOCK_STREAM,0)) < 0)
105         ERR_EXIT("socket");
106 
107     struct sockaddr_in servaddr;
108     memset(&servaddr, 0, sizeof(servaddr));
109     servaddr.sin_family = AF_INET;
110     servaddr.sin_port = htons(5188);
111     servaddr.sin_addr.s_addr = htonl(INADDR_ANY);
112 
113     int on;
114     if(setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR, &on, sizeof(on)) < 0)
115         ERR_EXIT("setsockopt");
116     if(bind(listenfd,(struct sockaddr*)&servaddr,sizeof(servaddr)) < 0)
117         ERR_EXIT("bind");
118     if(listen(listenfd,SOMAXCONN) < 0)
119         ERR_EXIT("listen");
120     struct sockaddr_in peeraddr;
121     socklen_t peerlen = sizeof(peeraddr);
122     int conn;
123 
124     pid_t pid;
125     while(1)
126     {
127         if((conn = accept(listenfd,(struct sockaddr*)&peeraddr,&peerlen)) < 0)
128             ERR_EXIT("accept");
129         printf("ip=%s,port=%d	
",inet_ntoa(peeraddr.sin_addr),ntohs(peeraddr.sin_port));
130 
131         pid = fork();
132         if(pid == -1)
133             ERR_EXIT("fork");
134         if(pid == 0)
135         {
136             close(listenfd);
137             do_service(conn);
138             exit(EXIT_SUCCESS);
139         }
140         else
141             close(conn);
142     }
143     return 0;    
144 }

View Code

client

  1 #include <stdio.h>
  2 #include <errno.h>
  3 #include <string.h>
  4 #include <stdlib.h>
  5 #include <unistd.h>
  6 #include <sys/types.h>
  7 #include <sys/socket.h>
  8 #include <netinet/in.h>
  9 #include <arpa/inet.h>
 10 
 11 #define ERR_EXIT(m)
 12     do{
 13         perror(m);
 14         exit(EXIT_FAILURE);
 15     }while(0)
 16 
 17 ssize_t readn(int fd, void* buf,size_t count)
 18 {
 19     size_t nleft = count;
 20     ssize_t nread;
 21     char *bufp = (char*)buf;
 22     
 23     while(nleft > 0)
 24     {
 25         if((nread = read(fd,bufp,nleft)) < 0)
 26         {
 27             if(errno == EINTR)
 28                 continue;
 29             return -1;
 30         }
 31         else if(nread == 0)
 32         {
 33             return count-nleft;
 34         }
 35         
 36         bufp += nread;
 37         nleft -= nread;
 38     }
 39     return count;
 40 }
 41 
 42 ssize_t writen(int fd, void* buf,size_t count)
 43 {
 44     size_t nleft = count;
 45     ssize_t nwrite;
 46     char *bufp = (char*)buf;
 47     
 48     while(nleft > 0)
 49     {
 50         if((nwrite = write(fd,bufp,nleft)) < 0)
 51         {
 52             if (errno = EINTR)
 53                 continue;
 54             return -1;
 55         }
 56         else if(nwrite == 0)
 57             continue;
 58         bufp += nwrite;
 59         nleft -= nwrite;
 60     }    
 61     return count;
 62 }
 63 
 64 void do_service(int conn)
 65 {
 66     char recvbuf[1024];
 67     while(1)
 68     {
 69         memset(recvbuf,0,sizeof(recvbuf));
 70         int ret = read(conn,recvbuf,sizeof(recvbuf));
 71         if(ret ==0)
 72         {
 73             printf("client close
");
 74             break;
 75         }
 76         else if(ret == -1)
 77             ERR_EXIT("read");
 78         fputs(recvbuf,stdout);
 79         write(conn,recvbuf,ret);
 80     }
 81 }
 82 
 83 struct packet
 84 {
 85     int len;
 86     char buf[1024];
 87 };
 88 
 89 int main(void)
 90 {
 91     int sock;
 92     if((sock= socket(AF_INET,SOCK_STREAM,0)) < 0)
 93         ERR_EXIT("socket");
 94 
 95     struct sockaddr_in servaddr;
 96     memset(&servaddr, 0, sizeof(servaddr));
 97     servaddr.sin_family = AF_INET;
 98     servaddr.sin_port = htons(5188);
 99     servaddr.sin_addr.s_addr = inet_addr("127.0.0.1");
100 
101     if(connect(sock,(struct sockaddr*)&servaddr, sizeof(servaddr)) < 0)
102         ERR_EXIT("connect");
103 
104     struct packet sendbuf;
105     struct packet recvbuf;
106     memset(&sendbuf,0,sizeof(sendbuf));
107     memset(&recvbuf,0,sizeof(recvbuf));
108 
109 //    char sendbuf[1024] = { 0 };
110 //    char recvbuf[1024] = { 0 };
111     int n;
112     while(fgets(sendbuf.buf,sizeof(sendbuf.buf),stdin) != NULL)
113     {
114         n = strlen(sendbuf.buf);
115         
116         sendbuf.len =htonl(n);
117         writen(sock,&sendbuf.len,4+n);
118         //writen(sock,sendbuf,strlen(sendbuf));
119         int ret = readn(sock,&recvbuf.len,4);
120         if(ret == -1)
121             ERR_EXIT("readn");
122         else if(ret < 4)
123         {
124             printf("client close");
125             break;
126         }
127         n = ntohl(sendbuf.len);
128         ret = readn(sock,&recvbuf.buf,n);
129         if(ret == -1)
130             ERR_EXIT("readn");
131         else if(ret < n)
132         {
133             printf("client close
");
134             break;
135         }
136         
137         fputs(recvbuf.buf,stdout);
138 //        fputs(recvbuf,stdout);
139 
140         memset(&sendbuf,0, sizeof(sendbuf));
141         memset(&recvbuf,0, sizeof(recvbuf));
142     }
143     close(sock);
144     return 0;    
145 }

View Code

作者：长风 Email：844064492@qq.com QQ群：607717453 Git：https://github.com/zhaohu19910409Dz 开源项目：https://github.com/OriginMEK/MEK 本文版权归作者和博客园共有，欢迎转载，但未经作者同意必须保留此段声明，且在文章页面明显位置给出原文连接，否则保留追究法律责任的权利. 感谢您的阅读。如果觉得有用的就请各位大神高抬贵手“推荐一下”吧！你的精神支持是博主强大的写作动力。如果觉得我的博客有意思，欢迎点击首页左上角的“+加关注”按钮关注我！

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原文地址：https://www.cnblogs.com/zhaohu/p/8962006.html