Da ich keine passende Library gefunden haben, für das was ich vorhatte, habe ich selber eine entworfen. Falls andere auch etwas ähnliches benötigen veröffentliche ich sie hier unter BEER-WARE LICENSE.

Funktionen:

• Mit Server verbinden
• Auf Ping antworten
• Empfangene Zeilen an Callback-Funktion übergeben
• Channel joinen
• Channel verlassen
• Texte/Befehle senden

irclib.h

/*
* ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <l3akage@martinpoppen.de> wrote this file. As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return Martin Poppen
 * ----------------------------------------------------------------------------
 */

#ifndef IRCLIB_H
 #define IRCLIB_H

#include <stdarg.h>
 #include <string.h>
 #include <stdio.h>
 #include <stdlib.h>
 #include <netdb.h>
 #include <sys/types.h>
 #include <sys/socket.h>

#define DELAY 1
 #define RETRIES 3
 #define MAXSENDBUFFER 1024
 #define MAXRECVBUFFER 1024

// define for some output
 #undef DEBUG

void do_send(int socket, char *cmd, ...);
 int do_connect(char *host, char *port, char *nick, char *user, char *channel);
 int do_recv(int conn, void (*writeData)(char* data));
 void do_join(int conn, char* channel);
 void do_part(int conn, char* channel);
#endif

irclib.c

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <l3akage@martinpoppen.de> wrote this file. As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return Martin Poppen
 * ----------------------------------------------------------------------------
 */

#include "irclib.h"

// send some stuff
// format like printf
// needs socket
void do_send(int socket, char *cmd, ...) {
 char sbuf[MAXSENDBUFFER];
 va_list ap;
 va_start(ap, cmd);
 vsnprintf(sbuf, MAXSENDBUFFER, cmd, ap);
 va_end(ap);

#ifdef DEBUG
 printf("SEND: %s\n", sbuf);
 #endif
 // send it
 write(socket, sbuf, strlen(sbuf));
}

// connect to server
// needs:
// host irc.test.de
// port 6667
// nick botibot
// user botibot
// channel #test
int do_connect(char *host, char *port, char *nick, char *user, char *channel) {
 int conn;
 int retries = RETRIES;
 struct addrinfo hints;
 struct addrinfo *res;

memset(&hints, 0, sizeof hints);
	do {
		hints.ai_family = AF_INET;
		hints.ai_socktype = SOCK_STREAM;

		if(getaddrinfo(host, port, &hints, &res)) {
			sleep(DELAY);
			continue;
		}
		if((conn = socket(res->ai_family, res->ai_socktype, res->ai_protocol))<0) {
			sleep(DELAY);
			continue;
		}
		if((connect(conn, res->ai_addr, res->ai_addrlen))<0) {
			sleep(DELAY);
			continue;
		}
		break;
	} while (retries-->0);

	// if connected register with user and nick
	if(retries>0) {
		do_send(conn, "USER %s 0 0 :%s\r\n", user, user);
		do_send(conn, "NICK %s\r\n", nick);

		do_join(conn,channel);

		return conn;
	}else{
		return -1;
	}
}

// receive data
// answer on pint
// send every line to callback function
int do_recv(int conn, void (*writeData)(char* data)) {
	char rbuf[MAXRECVBUFFER];
	char *tmpbuf = malloc(sizeof(char));
	     tmpbuf[0] = '&#092;&#048;';
	char line[MAXRECVBUFFER+1];
	int answerlen, i;
	int linelen;

	// reads date until error
	while((answerlen = recv(conn, rbuf, MAXRECVBUFFER, 0))) {
		linelen = -1;
		rbuf[answerlen] = '&#092;&#048;';
		#ifdef DEBUG
			printf("RECV: %s\n",rbuf);
		#endif
		tmpbuf = realloc(tmpbuf, strlen(rbuf)+strlen(tmpbuf)+1);
		strcat(tmpbuf, rbuf);
		for(i=0;i<strlen(tmpbuf); i++) {
			linelen++;
			line[linelen] = tmpbuf[i];
			// line should end with \r\n
			if(i>0 && tmpbuf[i-1] == '\r' && tmpbuf[i] == '\n') {
				line[linelen-1] = '&#092;&#048;';
				// Ping? Pong!
				if(!strncmp(rbuf, "PING", 4)) {
					rbuf[1] = 'O';
					do_send(conn, rbuf);
				} else {
					writeData(line);
				}
				linelen = -1;
			}
		}
		line[linelen+1] = '&#092;&#048;';
		tmpbuf = realloc(tmpbuf, strlen(line)+1);
		// write incomplete lines to buffer
		memcpy(tmpbuf, line, strlen(line)+1);
		rbuf[0]='&#092;&#048;';
		line[0]='&#092;&#048;';
	}
	return -1;
}

// join channel
void do_join(int conn, char* channel) {
	do_send(conn, "JOIN :%s\r\n", channel);
}

// leave channel
void do_part(int conn, char* channel) {
        do_send(conn, "PART :%s\r\n", channel);
}

Ein Beispiel – example.c

/*
 * ----------------------------------------------------------------------------
 * "THE BEER-WARE LICENSE" (Revision 42):
 * <l3akage@martinpoppen.de> wrote this file. As long as you retain this notice you
 * can do whatever you want with this stuff. If we meet some day, and you think
 * this stuff is worth it, you can buy me a beer in return Martin Poppen
 * ----------------------------------------------------------------------------
 */

#include "irclib.h"
#include <stdio.h>

void printData(char *data) {
	printf("Line: %s\n",data);
}

int main(void ){
	int reconnects = 3;
	do{
		int connection = do_connect("irc.test.de", "6667", "botibot", "botibot", "#test");
		do_recv(connection, printData);
	}while(reconnects-->0);
	return 0;
}

Fragen, Verbesserungen, Kritik .. sind natürlich gerne gesehen und erwünscht.