标签：linux
网络是大端
发数据从低地址发， 先发的是 高位的数据。
收数据从高位收，先收到的数据存放到低地址。
TCP 是 流式的 所用套接字也是流式的
文件描述符
socket 是 IP 加 端口号
用到的函数：
int socket(int domain, int type, int protocol); int accept(int sockfd, struct sockaddr *addr, socklen_t *addrlen); #include <sys/socket.h> #include <netinet/in.h> #include <arpa/inet.h> int inet_aton(const char *cp, struct in_addr *inp); in_addr_t inet_addr(const char *cp); in_addr_t inet_network(const char *cp); char *inet_ntoa(struct in_addr in); struct in_addr inet_makeaddr(int net, int host); in_addr_t inet_lnaof(struct in_addr in);
查找头文件中的类型定义
grep -ER
练习代码：【服务器 阻塞式的 只能处理一个请求】
/******
* 阻塞式的
*
* **********/
#include<stdio.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <errno.h>
#include<string.h>
#include <arpa/inet.h>
//#include <unistd.h>
#define _PORT_ 9999
#define _BACKLOG_ 10 // 监听端口 队列长度
int main()
{
int sock = socket(AF_INET, SOCK_STREAM, 0);
if (sock < 0)
{
printf("create socket error, error is : %d, errstring is : %s\n", errno, strerror(errno));
return 1;
}
struct sockaddr_in server_socket;
struct sockaddr_in client_socket;
bzero(&server_socket, sizeof(server_socket));
server_socket.sin_family = AF_INET;
server_socket.sin_addr.s_addr = htonl(INADDR_ANY);
server_socket.sin_port = htons(_PORT_);
if (bind(sock, (struct sockaddr*)&server_socket, sizeof(struct sockaddr_in)) < 0)
{
printf("bind error, error code is : %d, errno string is :%s\n", errno, strerror(errno));
close(sock);
return 2;
}
if (listen(sock, _BACKLOG_) < 0)
{
printf("listen error , errno code is :%d, errno string is :%s\n", errno, strerror(errno));
close(sock);
return 3;
}
printf("bind and listen success, wait accept...\n");
while (1)
{
socklen_t len = 0;
int client_sock = accept(sock, (struct sockaddr *)&client_sock, &len);
if (client_sock < 0)
{
perror("accept");
close(sock);
return 4;
}
char buf[1024];
memset(buf, ‘\0‘, sizeof(buf));
inet_ntop(AF_INET, &client_socket.sin_addr, buf, sizeof(buf));
printf("get connect, ip is :%s port is : %d\n", buf,ntohs(client_socket.sin_port));
while (1)
{
memset(buf, ‘\0‘, sizeof(buf));
read(client_sock, buf, sizeof(buf) - 1);
printf("client : %s\n", buf);
printf("server :");
memset(buf, ‘\0‘, sizeof(buf));
// fgets(buf, sizeof(buf), stdin);
// buf[strlen(buf) - 1] = ‘\0‘;
write(client_sock, buf, strlen(buf)+1);
printf("please wait...\n");
}
}
close(sock);
return 0;
}运行：
查看监听状态
[bozi@localhost ~]$ netstat -nltp (Not all processes could be identified, non-owned process info will not be shown, you would have to be root to see it all.) Active Internet connections (only servers) Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name tcp 0 0 0.0.0.0:9999 0.0.0.0:* LISTEN 10091/./server_1_si tcp 0 0 0.0.0.0:111 0.0.0.0:* LISTEN - tcp 0 0 192.168.122.1:53 0.0.0.0:* LISTEN - tcp 0 0 0.0.0.0:22 0.0.0.0:* LISTEN - tcp 0 0 0.0.0.0:60790 0.0.0.0:* LISTEN - tcp 0 0 127.0.0.1:631 0.0.0.0:* LISTEN - tcp 0 0 127.0.0.1:25 0.0.0.0:* LISTEN - tcp 0 0 :::47946 :::* LISTEN - tcp 0 0 :::111 :::* LISTEN - tcp 0 0 :::22 :::* LISTEN - tcp 0 0 :::23 :::* LISTEN - tcp 0 0 ::1:631 :::* LISTEN - tcp 0 0 ::1:25 :::* LISTEN -
测试的时候 用 telnet
telnet CTRL+] 就可以进入命令行了
问题描述：服务器与 客户端连接后 马上 kill掉服务器 然后又启动服务器 出现 Address already in use的错误 linux中等上半分钟 就可以启动服务器了
[bozi@localhost tcp]$ ./server_1_simple
bind and listen success, wait accept...
get connect, ip is :13.0.0.0 port is : 1032
^C
[bozi@localhost tcp]$ ./server_1_simple
bind error, error code is : 98, errno string is :Address already in use
原因：
解决方法：
练习代码：【客户端 】
#include<stdio.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <string.h>
#include <errno.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#define SERVER_PORT 9999
//#define SERVER_IP "192.168.0.1"
int main(int argc, char *argv[])
{
if (argc != 2)
{
printf("usage:server IP\n");
return 1;
}
char* str_server_ip = argv[1];
char buf[1024];
memset(buf, ‘\0‘, sizeof(buf));
struct sockaddr_in server_sock;
int sock = socket(AF_INET, SOCK_STREAM, 0);
bzero(&server_sock, sizeof(server_sock));
server_sock.sin_family = AF_INET;
//inet_pton(AF_INET, str_server_ip, &server_sock.sin_addr);
//别的 写法
server_sock.sin_addr.s_addr = inet_addr(str_server_ip);
server_sock.sin_port = htons(SERVER_PORT);
int ret = connect(sock,(struct sockaddr*)&server_sock, sizeof(server_sock));
if (ret < 0)
{
perror("connect");
return 2;
}
printf("connect success...\n");
while (1)
{
printf("client:>");
fgets(buf, sizeof(buf), stdin);
buf[strlen(buf) - 1] = ‘\0‘; // 把‘\n‘ 置成‘\0‘
write(sock, buf, strlen(buf) + 1);
printf("please wait ...\n");
}
close(sock);
return 0;
}练习代码：【线程的方式 服务器代码：可以同时处理多个客户请求】
#include<stdio.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <stdlib.h>
#include <pthread.h>
#include <arpa/inet.h>
#include <unistd.h>
#include <string.h>
#define LISTEN_QUEUE_NUM 50
void* handler_data(void* arg)
{
int client_socket = (int)arg;
printf("create a new thread...new socket:%d\n", client_socket);
char buf[1024];
while (1)
{
ssize_t _s = read(client_socket, buf, sizeof(buf) - 1);
if (_s > 0)
{
buf[_s] = ‘\0‘;
printf("client %s\n", buf);
write(client_socket, buf, strlen(buf));
}
else if (_s == 0) // client close
{
printf("client is close\n");
break;
}
else
{
break;
}
}
close(client_socket);
return (void*)0;
}
int main()
{
int listen_sock = socket(AF_INET, SOCK_STREAM, 0);
if (listen_sock < 0)
{
perror("socket");
exit(1);
}
struct sockaddr_in local;
local.sin_family = AF_INET;
local.sin_port = htons(9999);
local.sin_addr.s_addr = htonl(INADDR_ANY);
// local.sin_addr.s_addr = inet_addr("192.168.1.1");
//
if (bind(listen_sock,(struct sockaddr*)&local, sizeof(local)) < 0)
{
perror("bind");
exit(2);
}
if (listen(listen_sock, LISTEN_QUEUE_NUM) < 0)
{
perror("listen");
exit(3);
}
struct sockaddr_in peer;
socklen_t len = sizeof(peer);
// signal(SIGCHLD, collect_child);
while (1)
{
int new_fd = accept(listen_sock, (struct sockaddr*)&peer, &len);
if (new_fd > 0)
{
pthread_t tid ;
pthread_create(&tid, NULL, handler_data, (void*)new_fd);
pthread_detach(tid);
}
}
close(listen_sock);
return 0;
}练习代码：【客户端代码】
#include<stdio.h>
#include <sys/types.h> /* See NOTES */
#include <sys/socket.h>
#include <string.h>
#include <stdlib.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void usage(const char *proc)
{
printf("%s [ip] [port]\n", proc);
}
int main(int argc, char *argv[])
{
if (argc != 3)
{
usage(argv[0]);
return 3;
}
int conn = socket(AF_INET, SOCK_STREAM, 0);
if (conn < 0)
{
perror("socket");
return 1;
}
struct sockaddr_in remote;
remote.sin_family = AF_INET;
remote.sin_port = htons(atoi(argv[2]));
remote.sin_addr.s_addr = inet_addr(argv[1]);
if (connect(conn, (struct sockaddr*)&remote, sizeof(remote)) < 0)
{
perror("connect");
return 2;
}
char buf[1024];
while(1)
{
ssize_t _s = read(0, buf, sizeof(buf) - 1);
if (_s > 0)
{
//buf[_s - 1] = ‘\0‘;// 去掉\n
buf[_s] = ‘\0‘;
write(conn, buf, strlen(buf));
read(conn , buf, sizeof(buf) - 1);
printf("server echo : %s\n", buf);
}
else
{
perror("read ----");
break;
}
}
return 0;
}练习代码：【服务器 是 进程实现的】
#include<stdio.h>
#include <stdlib.h>
#include <string.h>
#include <signal.h>
#include <sys/socket.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void collect_child(int sig)
{
while (waitpid(-1, 0, WNOHANG) > 0)
{
printf("collect child done...\n");
}
}
int main()
{
int listen_sock = socket(AF_INET, SOCK_STREAM , 0);
if (listen_sock < 0)
{
perror("listen ");
exit(1);
}
struct sockaddr_in local;
local.sin_family = AF_INET;
local.sin_port = htons(9999);
local.sin_addr.s_addr = htonl(INADDR_ANY);
if (bind(listen_sock, (struct sockaddr*)&local, sizeof(local)) < 0)
{
perror("bind ");
exit(2);
}
if (listen(listen_sock, 20) < 0) // backlog 20
{
perror("listen");
exit(3);
}
struct sockaddr_in peer;
socklen_t len = sizeof(peer);
signal(SIGCHLD, collect_child); //////////////////////
while (1)
{
int new_fd = accept(listen_sock, (struct sockaddr*)&peer, &len);
if (new_fd < 0)
{
perror("accept");
exit(4);
}
pid_t id = fork();
if (id == 0)
{
// child
printf("fork done... pid : %d, get a new client: socket >%s:%d\n", getpid(), inet_ntoa(peer.sin_addr), ntohs(peer.sin_port));
char buf[1024];
while (1)
{
ssize_t _s = read(new_fd, buf, sizeof(buf) - 1);
if (_s > 0)
{
buf[_s] = ‘\0‘;
printf("client: %s\n", buf);
write(new_fd,buf, strlen(buf) );
}
else if (_s == 0)
{
printf("client is close\n");
break;
}
else
{
break;
}
}
close(new_fd);
exit(0);
}
else
{
// father
close(new_fd);
}
}
}练习代码：【客户端】
#include<stdio.h>
#include <stdlib.h>
#include <string.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <unistd.h>
#include <netinet/in.h>
#include <arpa/inet.h>
void usage(const char *proc)
{
printf("%s [ip] [port]\n", proc);
}
int main(int argc, char* argv[])
{
if (argc != 3)
{
usage(argv[0]);
return 3;
}
int conn = socket(AF_INET, SOCK_STREAM, 0);
if (conn < 0)
{
perror("socket");
return 1;
}
struct sockaddr_in remote;
remote.sin_family = AF_INET;
remote.sin_addr.s_addr = inet_addr(argv[1]);
remote.sin_port = htons(atoi(argv[2]));
if (connect(conn, (struct sockaddr*)&remote, sizeof(remote)) < 0)
{
perror("connect");
return 2;
}
char buf[1024];
while (1)
{
ssize_t _s = read(0, buf, sizeof(buf) - 1);
if (_s > 0)
{
buf[_s] = ‘\0‘;
write(conn, buf, strlen(buf));
read(conn, buf, sizeof(buf) - 1);
printf("server echo:%s\n", buf);
}
else
{
exit(55);
}
}
close(conn);
return 0;
}运行结果：
[bozi@localhost tcp3]$ netstat -alpt Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name ............................................. tcp 0 0 localhost:distinct localhost:56683 ESTABLISHED 3451/./server tcp 0 0 localhost:56683 localhost:distinct ESTABLISHED 3450/./client tcp 1 0 192.168.174.158:60487 ip-42-99-128-139.pacne:http CLOSE_WAIT 2969/clock-applet tcp 0 0 localhost:56682 localhost:distinct ESTABLISHED 3411/./client tcp 0 0 localhost:distinct localhost:56682 ESTABLISHED 3412/./server
udp编程
UDP（User Datagram Protocol，用户数据报协议）是一个简单的、面向数据报的无连接协议，提供了快速但不一定可靠的传输服务。
UDP与TCP相比主要有以下区别。
1．UDP速度比TCP快
由于UDP不需要先与对方建立连接，也不需要传输确认，因此其数据传输速度比TCP快得多。
2．UDP有消息边界
使用UDP不需要考虑消息边界问题，使用上比TCP简单
3．UDP可以一对多传输
利用UDP可以使用广播或组播的方式同时向子网上的所有客户发送信息。这一点也比TCP方便。
4．UDP可靠性不如TCP
与TCP不同，UDP并不提供数据传送的保证机制。如果在从发送方到接收方的传递过程中出现数据报的丢失，协议本身并不能做出任何检测或提示。因此，通常人们把UDP称为不可靠的传输协议。
5．UDP不像TCP那样能保证有序传输
UDP不能确保数据的发送和接收顺序。对于突发性的数据报，有可能会乱序。事实上，UDP的这种乱序性基本上很少出现，通常只会在网络非常拥挤的情况下才有可能发生
1）创建socket时，数据格式为：SOCK_DGRAM(数据块)
2）数据收发用recvfrom和sendto
ssize_t recvfrom(int socket,void *restrict buffer,size_t length,int flags,struct sockaddr * restrict address,socklen_t *restrict address_len);
restrict:类型限定符，限定约束指针。表明该指针是访问这个数据队形的唯一的方式
补充一点：
void *memcpy( void * restrict dest ,const void * restrict src,sizi_t n) 这是一个很有用的内存复制函数，由于两个参数都加了restrict限定，所以两块区域不能重叠，即 dest指针所指的区域，不能让别的指针来修改，即src的指针不能修改. 相对应的别一个函数 memmove(void *dest,const void * src,size_t)则可以重叠。
socket: 已连接的套接字
buffer：接收数据的缓冲区
length：缓冲区长度
flags ：调用操作方式
address:指向装有源地址的缓冲区（传出型参数）
address_len:指向源地址缓冲区的实际长度（传入传出型参数）
ssize_t sendto(int socket,const void*buffer,size_t length,int flags,struct sockaddr* dest_addr,socklen_t len);
socket:已连接套接字
buffer:包含待发送数据的缓冲区
length:buffer缓冲区数据的长度
flags:调用方式标志位
dest_addr:指向目的套接字的地址
len：dest_addr所指地址的长度
练习代码：【服务器 】
#include<stdio.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <string.h>
#include <stdlib.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define BF_SIZE 1024
int main(const int argc,const char* argv[])
{
if (argc != 3)
{
printf("please enter %s [ip] [port]\n",argv[0]);
exit(1);
}
int fd = socket(AF_INET, SOCK_DGRAM,0 );//SOCK_DGRAM 数据报套接口
if (fd < 0)
{
perror("socket");
exit(2);
}
struct sockaddr_in local;
local.sin_family = AF_INET;
local.sin_addr.s_addr = inet_addr(argv[1]);
local.sin_port = htons(atoi(argv[2]));
if (bind(fd, (struct sockaddr*)&local, sizeof(local)) < 0)
{
perror("bind");
return 2;
}
struct sockaddr_in remote;
socklen_t len = sizeof(remote);
while (1)
{
char buf[BF_SIZE];
memset(buf, ‘\0‘, sizeof(buf));
ssize_t _s = recvfrom(fd, buf, sizeof(buf) - 1, 0, (struct sockaddr *)&remote, &len);// 注意len取地址 sendto 中不用
if (_s > 0)
{
printf("client :[ip:%s][port:%d] %s", inet_ntoa(remote.sin_addr), ntohs(remote.sin_port), buf);
}
else if (_s == 0)
{
printf("read done...\n");
}
else
{
break;
}
}
close(fd);
return 0;
}练习代码：【客户端】
#include<stdio.h>
#include <stdlib.h>
#include <sys/types.h>
#include <sys/socket.h>
#include <arpa/inet.h>
#include <netinet/in.h>
#include <string.h>
int main(const int argc,const char* argv[] )
{
if (argc != 3)
{
printf("please enter %s [ip] [port]\n", argv[0]);
return 1;
}
int fd = socket(AF_INET, SOCK_DGRAM, 0);
if (fd < 0)
{
perror("socket");
return 2;
}
int port = atoi(argv[2]);
struct sockaddr_in remote;
remote.sin_family = AF_INET;
remote.sin_addr.s_addr = inet_addr(argv[1]);
remote.sin_port = htons(port);
while (1)
{
char buf[1024];
ssize_t _s = read(0, buf, sizeof(buf) - 1);
if (_s > 0)
{
buf[_s] = ‘\0‘;
}
_s = sendto(fd, buf, strlen(buf),0, (struct sockaddr*)&remote, sizeof(remote));
}
return 0;
}运行：
[bozi@localhost ~]$ netstat -atup Proto Recv-Q Send-Q Local Address Foreign Address State PID/Program name ....... udp 0 0 localhost:distinct32 *:* 4671/./server udp 0 0 *:60703 *:* 4673/./client
本文出自 “城市猎人” 博客，请务必保留此出处http://alick.blog.51cto.com/10786574/1836297
标签：linux
原文地址：http://alick.blog.51cto.com/10786574/1836297
