socket创建流程及代码示例

socket操作

1.1 创建socket

int socket(int domain, int type, int protocol);

domain: 确定通信的特性

AF_INET IPv4因特网域

AF_INET6 IPv6因特网域

AF_UNIX UNIX域

AF_UNSPEC 未指定

type: 指定套接字的类型

SOCK_DGRAM 长度固定的、无连接的不可靠报文传递

SOCK_RAW IP协议的数据报接口(POSIX.1中可选)

SOCK_SEQPACKET 长度固定、有序、可靠的面向连接报文传递

SOCK_STREAM 有序、可靠、双向的面向连接字节流

protocol参数通常是0，表示按给定的域和套接字类型选择默认协议。当同一域和套接字类型支持多个协议的时候，可以使用protocol参数选择一个特定的协议。

AF_INET通信域中套接字类型SOCK_STREAM的默认协议是TCP(传输控制协议)

AF_INET通信与中套接字类型SOCK_DGRAM的默认协议是UDP(用户数据报协议)

1.2 绑定地址(server)

int bind(int sockfd, const struct sockaddr *my_addr, socklen_t addrlen);

sockfd: 要绑定的套接字

my_addr: 地址结构体

addrlen: 结构体长度，通常为sizeof(my_addr)

1.2.1 struct sockaddr

该结构体定义了地址信息

struct sockaddr_in {

sa_family_t sin_family;

in_port_t sin_port;

struct in_addr sin_addr;

};

1.2.2 网络字节转换

网络中的数据格式为大端，所以需要将小端存储的数据转换成为大端存储，一下为网络字节序和本地字节序(小端)之间转换函数

uint32_t htonl(uint32_t hostint32); /// host to net long(uint32_t)

uint16_t htons(uint16_t hostint16); /// host to net short(uint16_t)

uint32_t ntohl(uint32_t netint32); /// net to host long(uint32_t)

uint16_t ntohs(uint16_t netint16); /// net to host short(uint16_t)

1.2.3inet_pton

int inet_pton(int af, const char *src, void *dst);

将字符串类型的地址转换成为struct sockaddr_in::sin_addr类型

af: 通信特性

src: 地址字符串

dst:truct sockaddr_in::sin_addr类型，长度必需为sizeof(struct in_addr).

1.2.4 查询地址

#include <netdb.h>

struct hostent *gethostent(void); ///（打开主机数据文件）返回struct hostent

void endhostent(void); /// 关闭打开的主机数据文件

void sethostent(int stayopen); ///打开主机数据文件

struct hostent {

char *h_name; /// 主机名

char **h_aliases;

int h_addrtype;

int h_length;

char **h_addr_list;

. . .

};

设置地址的例子：

struct sockaddr_in laddr;

laddr.sin_family = AF_INET;

laddr.sin_port = hotns(atoi(SERVERPORT));

inet_pton(AF_INET, "0.0.0.0", &laddr.sin_addr);

1.3 建立连接(client)

int connect(int sockfd, const struct sockaddr* my_addr, socket_t addrlen);

sockfd: 套接字

my_addr: 想连接的服务器的地址

addrlen: 地址结构的长度，通常为sizeof(my_addr)

1.4 服务器宣告可以接受连接请求 listen

int listen(int sockfd, int backlog);

backlog: 该进程最大的入队连接请求数

1.5 获得连接请求并建立连接 accept

int accept(int sockfd,struct sockaddr*my_addr, socket_t*addrlen);

my_addr: 用户地址

addrlen: 用户地址长度

1.6 发数据(client)

ssize_t send(int sockfd, const void *buf, size_t nbytes, int flags);

sockfd: 套接字

buf: 要发送数据的buf

nbytes: buf长度

flags: 发送标识

MSG_DONTROUTE: 勿将数据路由出本地网络

MSG_DONTWAIT: 允许非阻塞操作

MSG_EOR: 如果协议支持，此为记录结束

MSG_OOB: 如果协议支持，发送外带数据

1.7 收数据(server)

ssize_t recv(int sockfd, void *buf, size_t nbytes, int flags);

sockfd: 套接字

buf: 接收数据的buf

nbytes: buf长度

flags: 发送标识

MSG_OOB: 如果协议支持，接收外带数据

MSG_PRRK: 返回报文内容而不真正取走报文

MSG_TRUNC: 即使报文被截断，要求返回的是报文的实际长度

MSG_WAITALL: 等待直到所有的数据可用(仅SOCK_STREAM)

mysocket.h

#ifndef MYSOCKET_H_INCLUDED

#define MYSOCKET_H_INCLUDED

#include <iostream>

#include <netdb.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <sys/types.h>

#define SERVERPORT "1234"

#define SERVERIP "127.0.0.1"

#define MAXBACKLOG 10

#define MAXIPSIZE 20

#define BUFMAXSIZE 1024*1024

#define WRITEFILEPATH "./recvFile"

#define READFILEPATH "./a.tgz"

using namespace std;

#endif // MYSOCKET_H_INCLUDED

client.cpp

#include "mysocket.h"

int main()

{

int iRet = 0;

int sockFd = 0;

struct sockaddr_in serverAddr;

sockFd = socket(AF_INET, SOCK_STREAM, 0);

char sendBuf[BUFMAXSIZE];

if (sockFd < 0) {

cout << "socket is error" << endl;

} else {

cout << "socket is ok" << endl;

}

serverAddr.sin_family = AF_INET;

serverAddr.sin_port = htons(atoi(SERVERPORT));

inet_pton(AF_INET, SERVERIP, &serverAddr.sin_addr);

iRet = connect(sockFd, (struct sockaddr*)&serverAddr, sizeof(serverAddr));

if (iRet < 0) {

cout << "connect is error." << endl;

} else {

cout << "connect is ok." << endl;

}

FILE *rfp = fopen(READFILEPATH, "rb+");

while(1) {

iRet = fread(sendBuf, 1, BUFMAXSIZE, rfp);

cout << "fork:fread ret = " << iRet << endl;

if (iRet < 0) {

cout << "fread is error" << endl;

break;

}

iRet = send(sockFd, sendBuf, iRet, 0);

if (iRet < BUFMAXSIZE) {

cout << "fread is eof" << endl;

break;

}

}

fclose(rfp);

return 0;

}

server.cpp

#include "mysocket.h"

int main()

{

int iRet = 0;

int sockFd = 0;

struct sockaddr_in serverAddr, clientAddr;

socklen_t clientLen = 0;

char clientIP[MAXIPSIZE];

char recvBuf[BUFMAXSIZE];

sprintf(recvBuf, "rm %s", WRITEFILEPATH);

system(recvBuf);

memset(recvBuf, 0, BUFMAXSIZE);

int recvLen = 0;

FILE *fp = NULL, *wfp = NULL;

sockFd = socket(AF_INET, SOCK_STREAM, 0); /// create socket

if (sockFd < 0) {

cout << "socket is error" << endl;

} else {

cout << "socket is ok" << endl;

}

serverAddr.sin_family = AF_INET;

serverAddr.sin_port = htons(atoi(SERVERPORT));

inet_pton(AF_INET, "0.0.0.0", &serverAddr.sin_addr);

iRet = bind(sockFd, (struct sockaddr*)&serverAddr, sizeof(serverAddr)); /// bind addr

if (iRet < 0) {

cout << "bind is error." << endl;

} else {

cout << "bind is ok." << endl;

}

iRet = listen(sockFd, MAXBACKLOG); /// listen

if (iRet < 0) {

cout << "listen is error." << endl;

} else {

cout << "listen is ok." << endl;

}

int newSd;

while(1) {

newSd = accept(sockFd, (struct sockaddr*)&clientAddr, &clientLen);

if (newSd < 0) {

cout << "accept is error : iRet = " << iRet << endl;

break;

}

inet_ntop(AF_INET, &clientAddr.sin_addr, clientIP, MAXIPSIZE);

cout << "client: " << clientIP << " : " << ntohs(clientAddr.sin_port) << " is connected" << endl;

if (fork() == 0) {

wfp = fopen(WRITEFILEPATH, "ab+");

fp = fdopen ( newSd, "r+" );

while (1) {

iRet = fread ( recvBuf, 1, BUFMAXSIZE, fp );

if (iRet <= 0) {

cout << "recv is done" << endl;

break;

}

fwrite(recvBuf, 1, iRet, wfp);

}

fclose(fp);

fclose(wfp);

}

sleep(1);

}

return 0;

}

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