linux c tcp p2p

江湖上一直都有这位哥哥的传说，也有很多人说自己就他的真身！

但是。。。

今天分享一下TCP连接的P2P demo，江湖的规矩也要与时俱进。。。

————————————————————————————————————

原理之步骤（原理说了也不是那个理，做NAT的不说，谁知道呢？还不如过程呢）

一．A，B连接打洞服务器S

二．S记录下A的公网IP和端口，记录下B的公网

IP和端口

三．S将A的公网IP和端口以及B的公网端口发给B

四．S将B的公网IP和端口发给A

五． S命令B向A的公网IP和端口发起connect(打洞)

六． S命令B在B的公网端口上监听A的连接(connect)

七．S命令A向B的公网IP和端口发出连接命令(connect

// server.c

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <signal.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <fcntl.h>

#include <errno.h>

typedef struct IP_PORT

{

char ip[64];

int port;

}IP_PORT;

void sigint(int signum)

{

if (SIGINT==signum)

{

exit(1);

}

}

int main()

{

int listenfd;

int value = 1;

socklen_t clilen;

struct sockaddr_in cliaddr, seraddr;

int sock_a, sock_b;

char tmpaddr[128], tmpaddr_port[128], tmpaddr_port_port[128];

signal(SIGINT, sigint);

listenfd = socket(AF_INET, SOCK_STREAM, 0);

if (-1==listenfd)

{

printf("socket -server error: %s\n", strerror(errno));

return 1;

}

// reuse socket's address

setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR|SO_REUSEPORT, &value, sizeof(value));

// set bind server

memset(&seraddr, 0, sizeof(seraddr));

seraddr.sin_family = AF_INET;

seraddr.sin_addr.s_addr = htonl(INADDR_ANY);

seraddr.sin_port = htons(8099);

if (-1==bind(listenfd, (struct sockaddr*)&seraddr, sizeof(seraddr)))

{

printf("bind -server error: %s\n", strerror(errno));

close(listenfd);

return 1;

}

if (-1==listen(listenfd, 5))

{

printf("listen -server error: %s\n", strerror(errno));

close(listenfd);

return 1;

}

sock_a = accept(listenfd, (struct sockaddr*)&cliaddr, &clilen);

if (-1==sock_a)

{

printf("accept -server error: %s\n", strerror(errno));

close(listenfd);

return 1;

}

inet_ntop(AF_INET, (void*)&cliaddr.sin_addr, tmpaddr, sizeof(tmpaddr));

sprintf(tmpaddr_port, "%s %d", tmpaddr, ntohs(cliaddr.sin_port));

sock_b = accept(listenfd, (struct sockaddr*)&cliaddr, &clilen);

if (-1==sock_b)

{

printf("accept -server error: %s\n", strerror(errno));

close(sock_a);

close(listenfd);

return 1;

}

sprintf(tmpaddr_port_port, "%s %d", tmpaddr_port, ntohs(cliaddr.sin_port));

write(sock_b, tmpaddr_port_port, strlen(tmpaddr_port_port)+1);

close(sock_b);

printf("cli_a IP PORT cli_b PORT: %s\n", tmpaddr_port_port);

inet_ntop(AF_INET, (void*)&cliaddr.sin_addr, tmpaddr, sizeof(tmpaddr));

sprintf(tmpaddr_port, "%s %d", tmpaddr, ntohs(cliaddr.sin_port));

write(sock_a, tmpaddr_port, strlen(tmpaddr_port)+1);

close(sock_a);

printf("cli_b IP PORT: %s\n", tmpaddr_port);

close(listenfd);

printf("exit -server\n");

return 0;

}

//cli_a.c

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <signal.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <fcntl.h>

#include <errno.h>

typedef struct IP_PORT

{

char ip[64];

int port;

}IP_PORT;

void sigint(int signum)

{

if (SIGINT==signum)

{

exit(1);

}

}

int main(int argc, char **argv)

{

struct sockaddr_in seraddr;

int sockfd;

char tmpaddr_port[128];

IP_PORT peer;

int len;

char tmpbuf[128];

signal(SIGINT, sigint);

if (2!=argc)

{

printf("CmdLine should be: cli_a <IP>\n");

return 1;

}

sockfd = socket(AF_INET, SOCK_STREAM, 0);

if (-1==sockfd)

{

printf("socket -cli_a error: %s\n", strerror(errno));

return 1;

}

memset(&seraddr, 0, sizeof(seraddr));

seraddr.sin_family = AF_INET;

inet_pton(AF_INET, argv[1], &seraddr.sin_addr);

seraddr.sin_port = htons(8099);

if (0>connect(sockfd, (struct sockaddr*)&seraddr, sizeof(seraddr)))

{

printf("connect main -cli_a error: %s\n", strerror(errno));

return 1;

}

if (0>read(sockfd, tmpaddr_port, 128))

{

printf("read main -cli_a error: %s\n", strerror(errno));

return 1;

}

sscanf(tmpaddr_port, "%s %d", peer.ip, &peer.port);

// close main socket

close(sockfd);

// create new p2p client socket

sockfd = socket(AF_INET, SOCK_STREAM, 0);

if (-1==sockfd)

{

printf("socket -cli_a error: %s\n", strerror(errno));

return 1;

}

inet_pton(AF_INET, peer.ip, &seraddr.sin_addr);

seraddr.sin_port = htons(peer.port);

printf("Peer cli_b IP PORT: %s %d\n", peer.ip, peer.port);

// wait for cli_b to punch hole to cli_a self and cli_b is in accepting

sleep(5);

if (0>connect(sockfd, (struct sockaddr*)&seraddr, sizeof(seraddr)))

{

printf("connect p2p -cli_a error: %s\n", strerror(errno));

close(sockfd);

return 1;

}

len = write(sockfd, "I am a\n", strlen("I am a\n")+1);

if (0>=len)

{

printf("write p2p -cli_a error: %s\n", strerror(errno));

close(sockfd);

return 1;

}

len = read(sockfd, tmpbuf, 128);

if (0<len)

{

printf("%s", tmpbuf);

printf("\n");

}

close(sockfd);

printf("exit -cli_a\n");

return 0;

}

//cli_b.c

#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <unistd.h>

#include <signal.h>

#include <sys/socket.h>

#include <arpa/inet.h>

#include <fcntl.h>

#include <errno.h>

typedef struct IP_PORT

{

char ip[64];

int port;

}IP_PORT;

void sigint(int signum)

{

if (SIGINT==signum)

{

exit(1);

}

}

int main(int argc, char **argv)

{

struct sockaddr_in seraddr, cliaddr;

socklen_t clilen;

int sockfd, listenfd;

unsigned int value = 1;

char tmpaddr_port_port[128];

IP_PORT peer;

int len;

char tmpbuf[128];

int port;

signal(SIGINT, sigint);

if (2!=argc)

{

printf("CmdLine should be: cli_b <IP>\n");

return 1;

}

sockfd = socket(AF_INET, SOCK_STREAM, 0);

if (-1==sockfd)

{

printf("socket -cli_b error: %s\n", strerror(errno));

return 1;

}

memset(&seraddr, 0, sizeof(seraddr));

seraddr.sin_family = AF_INET;

inet_pton(AF_INET, argv[1], &seraddr.sin_addr);

seraddr.sin_port = htons(8099);

if (0>connect(sockfd, (struct sockaddr*)&seraddr, sizeof(seraddr)))

{

printf("connect main -cli_b error: %s\n", strerror(errno));

return 1;

}

if (0>read(sockfd, tmpaddr_port_port, 128))

{

printf("read main -cli_b error: %s\n", strerror(errno));

return 1;

}

sscanf(tmpaddr_port_port, "%s %d %d", peer.ip, &peer.port, &port);

// close main socket

close(sockfd);

// create new p2p connect/listen socket

listenfd = socket(AF_INET, SOCK_STREAM, 0);

if (-1==listenfd)

{

printf("socket p2p connect -cli_b error: %s\n", strerror(errno));

return 1;

}

inet_pton(AF_INET, peer.ip, &seraddr.sin_addr);

seraddr.sin_port = htons(peer.port);

printf("Peer cli_a IP PORT: %s %d\n", peer.ip, peer.port);

// punch hole to cli_a

connect(listenfd, (struct sockaddr*)&seraddr, sizeof(seraddr));

printf("Punching hole is finished!\n");

// reuse socket's address

setsockopt(listenfd, SOL_SOCKET, SO_REUSEADDR|SO_REUSEPORT, &value, sizeof(value));

seraddr.sin_addr.s_addr = htonl(INADDR_ANY);

seraddr.sin_port = htons(port);

if (0>bind(listenfd, (struct sockaddr*)&seraddr, sizeof(seraddr)))

{

printf("bind p2p -cli_b error: %s\n", strerror(errno));

close(listenfd);

return 1;

}

if (0>listen(listenfd, 5))

{

printf("listen p2p -cli_b error: %s\n", strerror(errno));

close(listenfd);

return 1;

}

sockfd = accept(listenfd, (struct sockaddr*)&cliaddr, &clilen);

if (-1==sockfd)

{

printf("accept p2p -cli_b error: %s\n", strerror(errno));

close(listenfd);

return 1;

}

len = read(sockfd, tmpbuf, 128);

if (0<len)

{

printf("%s", tmpbuf);

printf("\n");

}

len = write(sockfd, "I am b\n", strlen("I am b\n")+1);

if (0>=len)

{

printf("write p2p -cli_b error: %s\n", strerror(errno));

close(sockfd);

close(listenfd);

return 1;

}

close(sockfd);

close(listenfd);

printf("exit -cli_b\n");

return 0;

}

//result

Finally:

这下，有需要的朋友去p2p吧！！！