網路程式設計學習之路
阿新 • • 發佈:2018-11-21
網路程式設計系列(1)
網路程式設計–建立tcp連線
一直都認為網路程式設計是一塊很重要的部分,之前沒有時間和門道來學習。這次心血來潮,開始學習socket程式設計。
這次只是簡單的建立了server和client之間的連線,期間也遇到一點問題,這次算是做個記錄。
目標:瞭解測試方法,掌握網路程式設計的具體api
驗證方法
執行server程式碼後,要測試server是否正常啟動且埠正常暴露出來。最簡單的方式,可以用telnet來測試
(0.0.0.0表示本地網路,如果要本地寫server/client,用該地址)
[email protected]:~/share/mycode/c++/client$ telnet 0.0.0.0 12351
Trying 0.0.0.0...
Connected to 0.0.0.0.
Escape character is '^]'
server端列印log如下,
[email protected]:~/share/mycode/c++/tcp-server$ ./bin/Debug/tcp-server socket fd is 3 local ip =0.0.0.0 accept connect success, client port=52426ip =127.0.0.1 newsockfd=4
同時也可以用netstat命令來檢查網路埠的狀態。其中12351是我的server端用到的埠
[email protected]:~/share/mycode/c++/tcp-server$ netstat -ta 啟用Internet連線 (伺服器和已建立連線的) Proto Recv-Q Send-Q Local Address Foreign Address State tcp 0 0 *:microsoft-ds *:* LISTEN tcp 0 0 *:12351 *:* LISTEN tcp 0 0 localhost:27017 *:* LISTEN tcp 0 0 localhost:mysql *:* LISTEN
問題
server在寫的過程中遇到的都是些基本的網路引數問題,比如struct sockaddr_in該 如何填寫。
在client連線server端時卻出現一個問題 connect failed: Connection refused???許可權?還是哪裡不對??
[email protected]:~/share/mycode/c++/client$ bin/Debug/client
local ip =0.0.0.0
connect failed: Connection refused
到網路上搜,一直沒有搜到答案。通過telnet測試,說明server端是沒有問題的,問題肯定在client端。後來檢查程式碼,列印埠號,發現了問題。打印出的埠竟然是0。
[email protected]:~/share/mycode/c++/client$ bin/Debug/client
sin port = 0
port = 0
local ip =0.0.0.0
connect failed: Connection refused
檢查sockaddr_in 的欄位型別,發現埠號是2位元組,而不是4位元組。所以我在進行大小端轉換時應該用htons,而不是用htonl。用htonl轉換後的埠號在賦值時,被截斷了,因此打印出的埠號是0。
server端
如下是server程式碼
#include <iostream>
#include <arpa/inet.h>
#include <err.h>
#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <stdlib.h>
#define PORT 12351
#define MAXSIZE 10240
using namespace std;
int main(int args, char *argv[])
{
// cout << "Hello world!" << endl;
int sockfd, newsockfd;
struct sockaddr_in server_addr;
struct sockaddr_in client_addr;
int sin_size, portnum;
char buf[MAXSIZE];
if((sockfd = socket(AF_INET, SOCK_STREAM, 0)) == -1){
fprintf(stderr, "create socket failed!");
strerror(errno);
exit(1);
}
std::cout<<"socket fd is " << sockfd <<std::endl;
bzero(&server_addr, sizeof(struct sockaddr_in));
server_addr.sin_port = htons(PORT);
server_addr.sin_family = AF_INET;
// server_addr.sin_addr.s_addr = htonl(INADDR_ANY);
server_addr.sin_addr.s_addr = inet_addr("0.0.0.0");
if( bind(sockfd, (struct sockaddr*)(&server_addr), sizeof(struct sockaddr))){
fprintf(stderr, "bind failed");
strerror(errno);
exit(2);
}
struct sockaddr_in local_addr;
int len;
if (getsockname(sockfd, (struct sockaddr *)&local_addr, (socklen_t* )&len) == 0) {
struct sockaddr_in* sin = (struct sockaddr_in*)(&local_addr);
// *port = sin->sin_port;
char addr_buffer[INET_ADDRSTRLEN];
void * tmp = &(sin->sin_addr);
if (inet_ntop(AF_INET, tmp, addr_buffer, INET_ADDRSTRLEN) == NULL){
cerr << "inet_ntop err";
return false;
}
printf("local ip =%s\n", addr_buffer);
}
if(listen(sockfd, 10) < 0){
fprintf(stderr,"listen failed");
strerror(errno);
exit(3);
}
sin_size = sizeof(struct sockaddr_in);
while(1){
if( (newsockfd = accept(sockfd, (struct sockaddr *) (&client_addr),(socklen_t*) &sin_size))< 0){
fprintf(stderr, "listen failed");
strerror(errno);
exit(3);
}
std::cout<<"accept connect success, client port=" << client_addr.sin_port<<
"ip =" <<inet_ntoa(client_addr.sin_addr)<<std::endl;
std::cout<< "newsockfd=" << newsockfd<<std::endl;
}
return 0;
}
client端程式碼
#include <iostream>
#include <string.h>
#include <stdlib.h>
#include <error.h>
#include <sys/socket.h>
#include <unistd.h>
#include <sys/types.h>
#include <netinet/in.h>
#include <arpa/inet.h>
#define MAXLINE 4096
using namespace std;
int main()
{
// cout << "Hello world!" << endl;
int sockfd, n;
sockfd = socket( AF_INET, SOCK_STREAM, 0);
if( -1 ==sockfd){
perror("create socket failed");
strerror(errno);
exit(errno);
}
struct sockaddr_in server;
memset(&server, 0, sizeof(struct sockaddr_in));
server.sin_family = AF_INET;
server.sin_port = htons(12351);
server.sin_addr.s_addr = inet_addr("0.0.0.0");//192.168.1.106
printf("sin port = %x\n" ,server.sin_port);
printf("port = %x\n " ,ntohs(server.sin_port));
struct sockaddr_in local_addr;
int len;
if (getsockname(sockfd, (struct sockaddr *)&local_addr, (socklen_t* )&len) == 0) {
struct sockaddr_in* sin = (struct sockaddr_in*)(&local_addr);
// *port = sin->sin_port;
char addr_buffer[INET_ADDRSTRLEN];
void * tmp = &(sin->sin_addr);
if (inet_ntop(AF_INET, tmp, addr_buffer, INET_ADDRSTRLEN) == NULL){
cerr << "inet_ntop err";
return false;
}
printf("local ip =%s\n", addr_buffer);
}
int res = 0 ;
res = connect(sockfd, (struct sockaddr* )&server, sizeof(server));
if(res == -1){
perror("connect failed");
strerror(errno);
exit(errno);
}
return 0;
}